Damn girl, I knew my mom and dad watched porn when I was five; though I didn't realize the implications of it until I was 10 (when I overheard it in the middle of the night again, the cheap little clips you sometimes can watch for free for a few minutes on TV. No internet back then!)
Some people are more open to it than others, be thankful your dad isn't a prude and the kind of guy who thinks you should button up your collar and never even /hint/ at watching two people kissing on tv.
As for it being sexist. Sorry, don't buy it, and I'm a chick. It's legit, it's legal, it's consensual and women make a career out of it. In my opinion you have no right to tell a woman what she is doing with her body, wrong or degrading. It is her right, not yours.