I started reading Gould's essays in Natural History in 1974. Since then I've read a couple dozen books on Darwin and evolution without encountering the phrase "bird sex."
You obviously need professional help.
These seem to be Freudian sexual anxieties behind the anti-Christian hysteria. The real question is why obsessing on pictures of imaginary prehistoric ape men ( and demanding that others do so) seems to relieve the anxieties for them. You would have to study when the adolescent crisis set in and what series of events led to the fixation on the prehistoric ape men mythology as a solution. Something makes them feel comforted by obsessing on pictures of large, imaginary, prehistoric ape men. It may be a little like the geeks and nerds who turn to comicbooks with images of ultra-muscular superheroes like Superman, Batman, Spiderman, Captain America, and the Flash. Just a little more like the Swamp Thing monster obsessions.
There's always some kid in middle school, usually awkward around girls, who can't stop talking about Bigfoot, Sasquatch, Lizardman, the Wolfman, or various other mythical boogiemen and rural swamp monsters. It seems to be of that type. Then you see a sickly Victorian neurasthenic like Huxley latching on to this with obsessive-compulsive fury. Something psychological -in abnormal psychology - seems to be behind this. Most normal people don't get this hysterical about their hairy monster fantasies. Or it goes away when they finish puberty.