I don't really understand what all the fuss is about. Does it really matter why he doesn't want people to add content to his characters? Those are his creations, and every author should have the right to keep them the way he wants them. If I was a writer for one of those games, and people added stuff to my characters that I hate (no matter if it's because of bad writing or content I don't like), or without at least asking me beforehand, I would be pissed too. Besides pregnancy is a quite specific fetish, and if he doesn't like it, or even hates it, he has the right to say that he doesn't want people to add this stuff to his characters.