if we talk in movie context then - PORN is a movie too what two consenting adult are doing is just fine .But moral & legal obligations prohibits us to watch it in public .Now take any movie -By law you can`t show it to or make pirate copy of it to open public due to legal restrictions ...point is There are always regulations that as humans we need to follow even in trivial matters or gains.
Religion isn`t about gain or loss.its about spiritual attachment and believe thats far more important then anything for its followers - doesn`t what they follow.Atheist believe in no god and will argue/debate with you for days to prove you r wrong.
Its matter of what you believe .
(its open ended discussion ...)