Threeblonde what a simplistic thing to say..
"if one person dislikes the other doing something,then its likely that they'l do it anyway,in secret!!"
Possibly not, if your relationship has any traces of mutual respect and trust.
Second Coming, i agree that you cannot stop men from watching porn, some will, some won't, that's life. However, if your husband/partner is doing it and you are not happy with that, I don't think you should pretend that you are.
If you really are cool with it great. But if you are not cool about it, but pretend that you are just to keep the peace, well then you do have low self esteem, because you are unable to assert yourself to your dh/dp.