This appeal presents the question of the proper scope of our review of a National Labor Relations Board (“NLRB”) decision 1 refusing to defer to an arbitration award. We conclude that the Board acted within its discretion in refusing to follow the arbitrator’s award in this case.

The controversy arises from the discharge of Richardson, an employee of Hawaiian Hauling Service, Ltd., (“HHS”), when Richardson called HHS’s general manager a liar at a grievance meeting. Before this incident, Richardson had been employed by HHS for 22 years and had served as a Teamsters Union Shop Steward for 14 years. HHS gave Richardson two warning letters in October, 1973. The first concerned a protracted leave of absence. The second concerned a charge that Richardson had displayed pornographic photographs on his desk in January, 1972, and May, 1973, which were said to have been discovered and ordered removed on October 3,1973, by Rogers, HHS’s vice president and general manager. On October 15, 1973, Richardson and the union business agent met with Rogers and Richardson’s immediate supervisor concerning the warning letters. Richardson contended that Rogers had been aware of the pictures and had condoned the display and that therefore the second warning letter should be rescinded. Rogers denied this, and Richardson called Rogers a liar. Rogers discharged him on the spot, admittedly on account of Richardson’s accusation. 2

The union grieved the discharge to arbitration, contending that Richardson’s conduct at the meeting was protected activity within the meaning of 29 U.S.C. § 157 . The arbitrator issued an unexplained award in which he ruled that “the discharge in question was proper.” 3 The Administrative Law Judge deferred to the award, the NLRB overturned that ruling by a divided vote, and HHS now petitions to deny enforcement.

NLRB deference to an arbitration award is now an integral part of the administration of federal labor law, but Board deference is nonetheless discretionary. As the Court noted in NLRB v. Plasterers’ Union :

Upon review in this court the question is therefore whether the NLRB abused its discretion in reaching its deferral decision. 4 (Machinists Local 1309 v. NLRB (9th Cir. 1976) 530 F.2d 849 ; Local 700, Machinists Union v. NLRB (2d Cir. 1975) 525 F.2d 237, 244 ; NLRB v. Longshoremen’s Union Local 27 (9th Cir. 1975) 514 F.2d 481, 483 ; Provision House Workers Union Local 274 v. NLRB (9th Cir. 1974) 493 F.2d 1249 ; Associated Press v. NLRB (1974) 160 U.S.App.D.C. 396 , 492 F.2d 662 , 666; NLRB v. Horn & Hardart Co. (2d Cir. 1971) 439 F.2d 674, 679 ; NLRB v. Auburn Rubber Co., Inc. (10th Cir. 1967) 384 F.2d 1, 3 . ) The Board has established criteria to guide its decision and to this extent self-imposed restraints limit its discretion. 5 In reviewing the Board, we must insure that it adheres to its own standards until they are properly changed by the Board. We will not deny enforcement unless the Board clearly departs from its own standards 6 or its standards are themselves invalid. (Ban-yard v. NLRB (D.C.Cir.1974) 164 U.S.App.D.C. 235 , 505 F.2d 342, 347 ; Provision House Workers, supra, at 1249; Horn & Hardart, supra, at 679; Auburn Rubber, supra, at 3 .)

The decision of the majority of the Board in this case squarely relied on the Spielberg criterion that deferral will be rejected if the arbitral award is repugnant to the purposes and policies of the National Labor Relations Act (“Act”). The majority of the Board thought that the effect of the award “substantially dilute[d] an employee’s right to fully present his case during grievance and arbitration proceedings” ( 219 NLRB No. 126 , at 3) by upholding a discharge of an employee who used the epithet “liar” during the grievance proceeding. The Board did not abuse its wide discretion in thus characterizing the effect of the arbitral decision and in refusing to defer to the award. 7 The Board’s decision was well within the rationale of Crown Central Petroleum Corp. v. NLRB (5th Cir. 1970) 430 F.2d 724 . As the Crown court appropriately observed, grievance meetings often generate high emotions. Shouting and profanity are common and are protected activities in this setting. 8 Petitioner argues that *677 Richardson’s epithet was itself a deliberate falsehood and thus not protected activity. This argument, however, misses the mark 9 for as the Board noted, “[w]hen Rogers asserted that he had not seen the material on Richardson’s desk, Richardson could only meaningfully pursue the grievance” by showing that Rogers’ version was false. ( 219 NLRB No. 126 , at 4-5). Because a large number of grievances turn on credibility, we think the Board was within its discretion when it viewed the dispute from the perspective of the possible chill on pursuing grievances and extended the Crown rationale to cover the facts before us.

ENFORCEMENT GRANTED.

. 219 NLRB No. 126 , 1974-75 CCH NLRB Decisions ¶ 16,065 (July 30, 1975).

. Id. at 2-3 & n.2.

. The parties stipulated that the award would only contain the arbitrator’s conclusions, that the award would not comment on any of the evidence, and that no transcript would be made of the hearing. This hearing was held prior to the Board’s decision in Electronic Reproduction Service Corp., 213 NLRB 758 , 1974-75 CCH NLRB Decisions ¶ 15,046 (1974), in which the Board changed its practice of refusing to defer to an award which gave no indication that the arbitrator actually ruled on the unfair labor practice issue. In Electronic Reproduction the NLRB acknowledged that most arbitration hearings are unrecorded and concluded that a decision whether or not a discharge was for “just cause” necessarily decides the statutory issue of discriminatory discharge. The decision was based upon a disapproval of the prior practice of withholding evidence in grievance proceedings for presentation before the Board.

Because of our decision that NLRB refusal to defer was proper under the standards of Spielberg Mfg. Co. (1955) 112 NLRB 1080 , we need not decide whether the Board must apply Electronic Reproduction to arbitration hearings conducted before the date of that decision and express no opinion on the merits of such application. Nor do we have to decide whether the Electronic Reproduction standard is valid. See Banyard v. NLRB (D.C.Cir.1974), 164 U.S.App.D.C. 235 , 505 F.2d 342 , 347-49 where the lack of an adequate written explanation for an award was held to require nondeferral.

. An NLRB decision can also be attacked on ' the basis that the decision, upon review of the record as a whole, was not supported by substantial evidence. Universal Camera Corp. v. NLRB (1951) 340 U.S. 474, 488, 492-96 , 71 S.Ct. 456 , 95 L.Ed. 456 . However, that issue is also not before us as HHS argues only that the Board made errors of law in applying 29 U.S.C. §§ 158 (a)(1), (b)(3), and that the Board’s deferral decision was an abuse of discretion.

. E. g., Spielberg Mfg. Co. (1955) 112 NLRB 1080 ; International Harvester Co. (1962) 138 NLRB 923 ; Collyer Insulated Wire (1971) 192 NLRB 837 ; Electronic Reproduction Service Corp. (1974) 213 NLRB 758 . See Note, “The NLRB and Deference to Arbitration,” (1968) 77 Yale L.J. 1191 for a survey of pre-1968 NLRB deferral practice.

. “We do not suggest that the Board can announce a policy regarding deference to arbitration and then blithely ignore it, thereby leading astray litigants who depend upon it. But it can change its mind or alter its standards for deference in some respects without necessarily engaging in conduct so blameworthy as to justify our calling it abuse of discretion” (Horn & Hardart, supra, 439 F.2d at 679 .)

. We are not free to substitute our judgment for the Board’s even if, as Board members, we might have thought that the minority members’ views were more persuasive. Cf. NLRB v. Truck Drivers Union (1957) 353 U.S. 87, 96-97 , 77 S.Ct. 643 , 1 L.Ed.2d 676 . See generally. Winter, “Judicial Review of Agency Decisions: The Labor Board and the Court,” 1968 Sup.Ct.Rev. 53.

. “Neither do we think the language [“damn lies” “these . . . damn lies” Crown Petroleum, 430 F.2d at 726 n.3] used by [the discharged employees] was so opprobrious as to carry them ‘beyond the pale’ of the Act’s protection. It has been repeatedly observed that passions run high in labor disputes and that epithets and accusations are commonplace. Grievance meetings arising out of disputes between employer and employee are not calculated to create an aura of total peace and tranquility where compliments are lavishly exchanged. Adding our disclaimer to that of the Board, we do not condone the conduct of [the employees] in the meeting, but we do not feel that the interests of collective bargaining will be served by the external imposition of a rigid standard of proper and civilized behavior.” Id. at 731 . *677 See also, American Telephone & Telegraph Co. v. NLRB (2d Cir. 1975) 521 F.2d 1159, 1161-62 (“A certain amount of salty language or defiance will be tolerated . . [in] a closed grievance committee meeting where participants, engaging behind closed doors in a frank ' discussion of differences, might be expected to exhaust some steam without adversely affecting the employer’s conduct of its business”).

. The authorities cited by petitioner are inapt because they do not involve activities during the course of the grievance procedure. Unlike representation campaigns and contract negotiations, grievance procedures are analogous to litigation.