Bro love your pop divas and live your truth, fuck the haters.
My stepdad has been a pop music fan all his life, loves Tay Tay and all of the others, and I've never thought any less of him, he's quite literally my best parent and friend by a wide margin. I'm also saying this as a person heavy into metal and rap, because we can all like what we enjoy without begrudging one another for it.
The best thing you can do is try and find a new therapist that you're comfortable with, once you find that partnership, if you find it, you'll feel better about yourself as hopefully that therapy partner will help make you feel better about yourself, like any good therapist should be working towards doing.
I'm sure your stepdad is a very good person. You're right that we should feel free to like what we want. Sometimes it feels hard to ignore the haters, but I'll try!
Unfortunately I'm stuck with this therapist for at least six months before he retires and is replaced by someone else. I can't afford another one which is not funded by disability support :(
I'm sorry you're dealing with that, we definitely need better mental health services, especially for autistic folks, my son is autistic as well and it's been hard finding support for him. I hope the next therapist does a better job, or that the situation changes and you can get more resources, either way don't let the haters get you down, stay strong.