Both. Yes, he probably didn't mean it and would not follow through on it, but it was intended and reads as a threat of rape.
"Offering" to violently *expletive deleted*ck a woman during an arguement and implying that she should like it because it will put her in her place and make her accept his side of the arguement is a pretty commen way that men threaten woman with rape, as well as being EXTREAMLY sexist.
You want to talk politics, talk politics, and if it decends into poo flinging, keep the poo related to the subject at hand. Insult his/her intellegnce, morals or personal politics all you want, but leave gender/race/sexual orintation the hell out of it.
I promise, any guy who offers up such a sentiment to me will have his ass verbally turned to grass in quick order.
I liked her responce (which also could be considered a threat) :)