I don't differentiate over Hetero, Gay, Lesbian or Animal sex on the screen. To me it is just uncomfortable to watch. Probably my age and the times I grew up in. The fact that I considered it porn might be an indicator of how out of touch I am with prevailing liberal attitudes towards simulated sex on screen.
OMG! Did I just call me a conservative? Nooooooooooooooooooooooooooooo !
PS - Putting it all out there, I'm not too fond of nudity in films either. Except for animals. Animals are OK nude, just not having (probably unsimulated) sex. :>)