YOU'RE 17 BLOODY FUCKING YEARS OLD!
Be a man and tell'em to piss off.
Ok I'm cooled down now.
You are your own person, They can't and shouldn't be controlling you.
You are a human being with your own thoughts feeling and beliefs. Who are they to tell you what you can and can't like.
Granted, they are your parent's, but being a brony is harmless.
That right there is the biggest load of shit i've ever heard in my entire life.
I'm sure at one point in your life you've asked for something your friend had and they said "no you can't get that." Or. "I dont care if your friend has one/is doing it i said no."
My immediate response tho that would have been. "Ok then. My friend smokes meth, does that make it ok to smoke meth then."
Again, they shouldn't be telling you what you can and cannot like. Especially if its something a harmless as a fandom.