They are your parents, and think about this, they can make your life miserable. But you shouldn't have to wait until you're out of the house to be happy.
Here's what you do, you listen to them, and make sure they know you heard them. You don't react, no matter how angry what they say makes you. You simply ask to talk about it. Everything they say, you repeat back to them in your own words. If they say, "The show is for little girls and it's wrong for you to watch," you say something like, "It's inappropriate to watch a show that's made for small girls when I am...(I actually don't know what you are sorry, a 17 year old boy?)," etc. until they are done. This lets them know you are being rational, are intelligent, and are in control of yourself. This is absolutely necessary before they can even begin to listen to you. After all, why should they listen to you when they know what's best and you aren't listening to them?
I would also stop buying merchandise and making it public for a while just so that they are no longer on edge. This isn't changing who you are, it's just giving them some space and allowing them to see you beyond your bronyness.
Anyway, then you can start addressing their concerns with the other advice given here. The thing is, you want something, so give a little something first. I think the biggest thing is to show you are in control of yourself and are respectful. There is tons of communications advice online that real family therapists use (I am a therapist actually) such as "I" statements and no blaming. Look these up, and just remember to breath and whatever you do, do not react!
I have been there before. Remember your relationship and communication with your parents is really the issue, not the show. Do you have any siblings that can help? Work on that first. Spend time with them and get on a friendly basis with them. Again, family therapy tools should be easy to find online and if not just ask. (Not that i am officially counseling you). One thing i want to make you aware of is that you have had a lot of ideas thrown at you here, but for the most part I have been seeing your response as lacking hope and insisting nothing will work. That is ok because some of the advice was really bad and you should be able to work out your feelings and ideas here, but Try to open your own mind up as well.
Again, Ive been there when I was in high school too. It is awful but in six years you will want to love your parents and have them as a part of your life. Im sure you even want that now.