WASHINGTON -- The latest smack-down of former Harvard President Lawrence Summers should extinguish any remaining doubt that political correctness is the new McCarthyism.

Summers, you'll recall, was driven out of his university post in 2005 after he suggested at a conference that gender differences might account for an underrepresentation by women in science, math and engineering.

Never mind that scientific evidence suggests as much. One simply doesn't say -- ever -- that men and women aren't equal in every way.

Summers' remarks were seized upon, taken out of context and misinterpreted by many, including one female biologist from MIT, who walked out on the president's talk, later saying that she felt she was either going to faint or throw up.

And we say there's no difference between men and women? Can you imagine a man bolting from the room with light head and upset tummy if a woman college president suggested that genetic differences might account for males lagging behind females in reading and writing?

Men, being the logical, bemused fellows that they mostly are, would probably say, "Hear, hear!" -- and wonder how much longer before lunch. Stomping out of the room in a tizzy is not in the adult male repertoire. (Could it be genes?)

For thinking improper thoughts, Summers the Blasphemer was banished into the outer darkness. There's no debating that he was punished for saying something that made a special group feel bad -- the new blacklisting offense. To be called a sexist, racist or homophobe today is tantamount to being a communist sympathizer 50-60 years ago.

Fast-forward to this month. Summers was scheduled to be the keynote speaker at the University of California Board of Regents bimonthly board meeting.

And then he wasn't.

Maureen Stanton, an evolution professor at UC Davis, was "stunned and appalled" when she learned of Summers' upcoming speech and circulated a petition to have his invitation withdrawn.

Sinning against the sisterhood not only isn't forgotten, apparently it isn't ever forgiven.

Summers' invitation was "not only misguided but inappropriate at a time when the university is searching for a new president and continues to build and diversify its community," the petition said.

One can't help wondering what those cultural principles might be if they don't include supporting free speech? As the university continues to build and diversify its community, will that mean diversity of thought or only diversity of gender identity and race?

The answers are implicit in the draconian reaction to Summers' invitation. Diversity on the American campus of today -- and increasingly in the broader culture -- means a multiculti rainbow of like-thinking people. Say or think incorrectly and one will be censored and potentially ruined.

Summers' original offense is shocking only if you ignore the fact that men excel in certain areas and women in others -- outcomes more likely related to our hunter-gatherer genes than to contemporary bias. Whatever the case, there's simply no denying that math giftedness is more prevalent among males, a fact some scientists surmise may have to do with testosterone exposure in the womb.

Blame the mother.

Meanwhile, if it helps mitigate nature's imbalance, we might consider that there are also more male than female mass murderers. If males get to boast Einstein, Newton and da Vinci, they also get to claim Attila, Hitler and Pol Pot.

Women who object to Summers' assertion can argue with facts, if they choose. One study found, for example, that women's scoring on math tests is influenced by whether they believe their performance is a function of genes or socialization.

Other studies also show that the gender gap in math is closing. None of these findings negate what science has otherwise revealed about boy and girl brains: They develop and operate differently.

University women do have a right to be concerned about how they are perceived as they compete with men for tenure, which women receive less often. Studies suggest that bias may play a role, but other research points to conflicts between family and career. The system may need tweaking for fairness and balance, but educators have a higher moral obligation to nurture the marketplace of ideas.

In Joseph McCarthy's day, academics were among the primary targets of the thought police, while women had barely earned a voice in the political arena. Of all who should rebel against the stifling of voices and unpopular ideas, university women should be leading the charge.

The best way to prove Summers wrong, meanwhile, is to prove him wrong.