If looking at porn is a replacement for actual contact with one's spouse, then of course it is a problem. For me, I could make love to my wife and then look at porn two hours later while she is sleeping. Then I'd want to make love to her again. Not that it was an option.......
I never looked at online porn when the sex was frequent, it was only when it was in the "once in a blue moon" phase. Does that make it right? Who knows. Taking spiritual beliefs out of it for now, it is wrong when one's spouse has serious objections to it, but you keep doing it anyway. I'm guilty of that, but didn't understand it at the time. My wife looks as good physically as most of the women in the pictures, better actually. However, she has some serious body image issues and thought I was drooling over very young women, which only made her own issues worse. That was horrible of me, and it drove a pretty big wedge between us. Funny though, she didn't mind the occasionaly video to watch in the bedroom while we were........you know.
I think a lot of guys look at it because it is there. Simple enough. Again, we're visual. Of course there are bigger issues. It's one of the biggest industries around, heck, porn built the internet. What degredation are we supporting? Anyone think the women (and men for that matter) are in this industry by choice? Doubtful. These women are somebody's daughter whose life took a terrible turn somewhere, and by viewing the images, or more so, paying for access, we are perpetuating the problem. Just another way to look at it.
For me, I can say I find it stimulating, I can admit that. I'm very visual and very sexual. However, I'd always rather have the real thing and porn would never, ever replace that. Now if I could just get my wife back, I'd be on the right path. But that's a whole 'nother story.