Holy fuck there are a shitload of sexually-repressed people on this stank hole of a planet.
Because it has nothing to do his "backing off", which simply means that when she expressed that she wasn't interested, he stopped the advances.
So, he's a piece of shit for treating her badly or for getting in the shower? What's the point of being cordial to someone who's not interested?
After a drunk night on the town, in a shared hotel room. As I mentioned earlier, it could very well be a case of drunken stupidity and/or mixed signals. Literally, all we have is her word to go on, which isn't saying a lot.