It's just another way to disrespect women. I've found that the same dudes who go on adn on about how great it is to fuck a chick in her butthole are repulsed and disgusted when you ask them if they've ever eaten out said butthole.
Oh not not too much hypocrisy going on there.
I don't know who you're talking to, but I would always have my tongue buried in my ex-girlfriend's ass before I fucked it. Once we started having anal sex, she always kept it squeaky clean, so there was really nothing disgusting about it.
As far as disrespecting women goes, I suppose it could be used that way. There's definitely a submissive element to the act. But submission can be as much about giving away control of your own body as it can be about taking it away from someone else. I don't see that there's any disrespect in a woman choosing to give a man an erotic gift.
And I think that applies in real life and in porn. Just as it was incredibly erotic to see my ex stick her ass up in the air and ask me to fuck it, it's also incredibly erotic to see a pornstar stick her ass up in the air and ask me (as the viewer) to watch her get fucked.