Yay, I'm here.
As far as 'tap that ass' goes, I always assumed it referred to the tapping sound made while having rear-entry intercourse. I think it's pretty safe to say that, if not the origin of the phrase, it's the way many other people interpret it, as well. It's much more correlative, in my opinion, than the 'tapping a keg' suggestion.
Now, this does suggest a very familiar objectification of a strange woman that, as a woman, I find to be stupid and presumptuous. But, as I've been told again and again and again here at TFP, this is just the way guys are. So be it. Stupid and presumptuous.
As for 'I'd hit that,' I've never thought about it in the context of violence or rape. More just an adaptation of 'I'd tap that' - another stupid and presumptuous remark made by men to gratify their own unfeasible fantasies and un
tapped masculinity.
Now, all that said, I realize that some perfectly nice guys make a habit out of saying these things, but personally, I would never really respect a man who said them as anything other than an occasional joke. Maybe a sign of maturity is knowing when to keep your trap shut. I dunno...