If the OP has come on this forum to get affirmation that her views on porn are right, then she's got that. If she's come on here seeking encouragement to end her marriage, she's got that too. Those of you who have said her and her husband are incompatible, or that she shouldn't forgive his transgression, or that she shouldn't trust him again... you've done a good job in encouraging her to end her marriage.
But is she on this forum because she wants to/intends to end her marriage...? Or is she here because she wants guidance on how they can try to save their marriage? From what I've read here, I'm assuming it's the latter, and so the thoughts I'm sharing are attempting to help her with this.
It's not as simple as her just walking away from her marriage. I'll explain why I think this: From what I've understood, they've been together ages, have invested a lot of time in building a life together, they have a child together, and otherwise have had a generally stable and secure relationship. Also, from what the OP has said, it sounds like she believes he is not cheating her, that he is not prone to lying in general, nor does she believe he 'gets off on the abuse and degradation' of women, she considers him to be very respectful of women. She seems to accept that not all people who enjoy porn enjoy it specifically for the abuse and degradation it engenders, and that some people just watch porn because they like watching two people have sex (I can personally vouch for this).
Whatever the dark connotations of porn, and however you feel about porn as an industry, the subjective intentions of the viewer must surely come into it, especially if you are familiar with their character and know them to not be abusive and disrespectful of women.
The lying is a bigger issue - as the OP herself has stated - but does it have to be a marriage-ending one? Or could they work through it? and if so, is there any better way of doing this than by starting to communicate better, and trying to understand each other's feelings and motivations better, instead of - as Offed put it - "thinking they get to dictate the terms of the relationship entirely by themselves and tell their partner how they are allowed to feel"...?
Because if either of them are doing this, it's not a true partnership. They both need to stop doing this, if they want to save their marriage. If anyone has a better suggestion for how they can start resolving this situation, then please do share. But I think it's going to take a little movement on both sides, a little more compassion and open-mindedness from both. Otherwise, yes, just accept you are incompatible and end the marriage.