You don't need feminism, you need to answer the most difficult answer ever.
Is it gay to be fucked in your ass by a girl?
Pro gay:
It's most likely a replica male penis
It's the way gays have sex (except they use their real dicks)
Pro straight:
Milking the prostate
You're having sex with a girl (AT LEAST SOMEONE WHO IDENTIFIES AS A GIRL LAWL)