In academic feuds, as in war, there is no telling how far people will go once the shooting starts.

Earlier this month, members of the International Academy of Sex Research, gathering for their annual meeting in Vancouver, informally discussed one of the most contentious and personal social science controversies in recent memory.

The central figure, J. Michael Bailey, a psychologist at Northwestern University, has promoted a theory that his critics think is inaccurate, insulting and potentially damaging to transgender women. In the past few years, several prominent academics who are transgender have made a series of accusations against the psychologist, including that he committed ethics violations. A transgender woman he wrote about has accused him of a sexual impropriety, and Dr. Bailey has become a reviled figure for some in the gay and transgender communities.

To many of Dr. Bailey’s peers, his story is a morality play about the corrosive effects of political correctness on academic freedom. Some scientists say that it has become increasingly treacherous to discuss politically sensitive issues. They point to several recent cases, like that of Helmuth Nyborg, a Danish researcher who was fired in 2006 after he caused a furor in the press by reporting a slight difference in average I.Q. test scores between the sexes.

“What happened to Bailey is important, because the harassment was so extraordinarily bad and because it could happen to any researcher in the field,” said Alice Dreger, an ethics scholar and patients’ rights advocate at Northwestern who, after conducting a lengthy investigation of Dr. Bailey’s actions, has concluded that he is essentially blameless. “If we’re going to have research at all, then we’re going to have people saying unpopular things, and if this is what happens to them, then we’ve got problems not only for science but free expression itself.”