We used a computer harassment paradigm to test the hypothesis that affirming the legitimacy of discrimination against homosexuals increases the likelihood that heterosexual men will engage in verbal gay bashing. Legitimacy of discrimination was varied among heterosexual males (N = 167) by suggesting that denying homosexuals rights and benefits is either illegitimate or legitimate, and participants interacted online with either a gay or straight bogus discussion partner. Results show that (a) participants sent more offensive comments when the legitimacy of discrimination against homosexuals was affirmed, and (b) legitimacy affected gay bashing through its effect on collective guilt. These findings suggest that challenging the legitimacy of discrimination can be an effective strategy for reducing outgroup derogation. Copyright © 2011 John Wiley & Sons, Ltd.