Why is my mom ok with sex/masterbation but not porn?

Why is it that so many parnets are ok with masterbation, but not porn? Sex is a natural thing. I hate how sex and nudity are generally looked down upon by society. And it's all because of bullshit like christianity. I hate my sociopathic, lunatic, christian mother. I wish I had athiest parents. Because at least they would actually support me expressing myself the way I want to. Idk what's so bad about porn, your just looking at people having sex. Which is pretty much what your gonna do someday anyway.