If that's what you mean, OP, can you explain what that comment about your friend leaving her husband was for? 
Anyway - no, I don't think it's as simple as making the assumption you have from I am saying that MN has a lot of posts about DW's hating porn and none about DW actively watching it with partners. Therefore, it could be assumed that its uncommon or frowned upon by DWs
People post things like that on MN because they have a problem with something, not because they are happy with something. A lot of women see porn use as something they will not accept, hence why they have started a thread about it. Just as a woman might start a thread about how she finds a DH getting so pissed he throws up on the floor unacceptable, or a DH putting his hobbies above family life.
People tend not to come on to MN and say "you know what, DH just made me an amazing dinner, then we went upstairs, watched some really hardcore porn and had a mind-blowing shag."
If you went by the assumptions you could make from reading just the original posts and problems on MN threads, then you could assume that most women are in relationships with men who never cook, or who don't give them enough financial support, or who go on 8 golfing holidays a year.
Ditto that posters either have immaculate show homes that they redecorate 3 times a year, or houses that haven't been cleaned or tidied since they moved in 6 years ago.