I have experienced this first hand as well and will never commit that naive mistake again.

See also the responses of women learning their partner is bisexual or their dating racial preferences.

Their mating strategy optimizes for status and in the process creates and reinforces the very structures they claim to oppose. What they are really opposing is the negative effects these structures have on them.

They are not evil or man-hating, but all of us are ruled by instinct way more than we would like to admit. And the people self aware enough to recognize and avoid reacting to them, specially when they relate to something as important as romantic relationships, are not very common.