Choice
I've got to admit that the idea of getting someone drunk in order to get them to try anal sex, when sober they wouldn't want to, is to my mind only a couple of steps removed from the area of date rape drugs. In that, I mean weakening somebody's willpower through a drug.
I know some people are going to call me for suggesting that getting someone drunk is akin to date rape. I know that people generally chose to get drunk, as opposed to sickos who give women flunitrazepam, ghb etc without their knowledge, but the iodea of getting someone intentionally drunk in order to get them to do something they would be opposed to while sober, just doesn't sit well in my mind (to me it seems like the first couple of steps down that road).
If a woman wanted to try anal sex, but had to get drunk to be comfortable with the physical side, then that's a different matter alltogether, and would be OK by me.
It's all about personal choice, not getting somebody so pissed that they don't have the mental faculties to resist a persistant request