@Linkat,
Well I'd have to give the caveat that if it was something like child pornography, or porn where someone was actually (and not just acting like) being forced they were doing something against their will. I'm including things like beastiality, where consent cannot be given.
It also isn't cool if someone is somehow making their partner watch too, if they don't want to.
But watching porn (in most cases) is no different to me than getting a better visual and auditory experience of what a person was thinking about in their heads, and just as private.