Cheating and the fault lies on the one who got cheated on.

So one of my friends thinks that if a person cheats or watches porn it's the fault of the one who got cheated on! They think that the cheater isn't getting enough attention or sex at home so they look for it elsewhere. As for porn it's because the partner isn't doing enough or something they specifically like. Now I don't believe this at all, but what is your opinion on it? To me she's just putting all the blame on the victim ( victim as in cheating wise not porn wise).