I am a feminist. I have marched at the barricades, subscribed to Ms. magazine, and knocked on many a door in support of progressive candidates committed to women's rights. Until a month ago, I would have expressed unqualified support for Title IX and for the Violence Against Women Act.

But that was before my son, a senior at a small liberal-arts college in New England, was charged—by an ex-girlfriend—with alleged acts of "nonconsensual sex" that supposedly occurred during...