"We believe this because we examined dozens of empirical studies, both published and unpublished, of team cohesion and performance in military units, industrial and sports teams and other groups. We also analyzed the political and organizational process by which African Americans were integrated into the military in the 1940s and 1950s, despite tenacious racial animosities among service personnel and vigorous opposition by military leadership. Further, we investigated how nondiscrimination policies for gays and lesbians are working in practice in U.S. police and fire departments and in Israeli and European military forces. Too often, this evidence is dismissed as irrelevant, without serious consideration or refutation. Indeed, a wealth of evidence, including the military's own research, debunks the claim that gays would irreparably damage "task cohesion." Liking all the members of one's group on an interpersonal level--"social cohesion"--either has no measurable influence on performance or, at very high levels, actually may have a detrimental impact. In short, the military learned long ago that professionalism does not require you to like someone to work effectively with him or her."