Presenting a new sub: r/TransPets

feel free to use this shitpost, I give up trying to get around the new account shadow ban

title: My dog is transphobic and I think I'm going to have him put down

I hope this isn't the wrong place to post this. I tried posting this to r/dogs and they deleted and banned me for some reason. I'm just trying to get some feedback this awful situation is giving me a lot of stress.

Two years ago I adopted a handsome male German Shepherd from a rescue organization. He's been badly abused in the past and for this reason he is extremely aggressive towards males. It took many months of hard work for him to warm up to me and for me to earn his trust after I adopted him. He is typically a real sweetheart around women though such as my sisters and nieces and past girlfriends so it has never been a problem in the past, I just can't really have male guests over. Other than his issues with men, he's been a wonderful dog for me. Very well behaved, very loving. He is my best friend! However, the dog has started to behave very irrationally lately. I recently started dating a transwoman and my dog is constantly misgendering her. He snarls, barks and terrifies my poor girlfriend as if she was a male. SHE IS A WOMAN! Last night she was over my place snuggling on the couch with me and she playfully smacked me. The dog came FLYING across the room and bit her arm! I had to take her to the ER the bite was so bad! I'm so completely embarrassed by this. I've screamed and hollered at my dog trying to get through to him that TRANSWOMEN ARE VALID WOMEN and that his misgendering of her is EXTREMELY PROBLEMATIC but it's no use, he just doesn't get it. I just don't know what to do. I thought about seeing if I can find another home for him, but nobody is going to want to adopt a transphobic dog. I think my only option at this point is to take him to the shelter to be euthanized as sad and depressing as that will be for me. Does anybody have any advice at all to make my dog less transphobic? I am completely desperate at this point.