Hmm...you'll have interactions like this every once in a while because you're playing with real people...not npcs. And Real people do unpredictable (and sometimes annoying) things....Welcome to MMO'S!

When stuff like this happens, I tend to brush it off when the dungeon's over and not let it eat at me. Because there are plenty of other awesome players and 9 times out of 10 I wont see them again.