Ernie had stepped into the commonroom from a long study session in the library and was greeted by rumors of a strange man running about. Upon hearing that he assumed two things: one, that they were speaking of Bole and that they didn't mean actually in Hufflepuff. He realized as he was walking up to his room, and heard Nicky scream, that he had been mistaken.
Not thinking twice, he pushed open the door and saw Stan attacking Nicky. Ernie didn't like Stan, but he honestly hadn't thought he would do something like this.
"what the he'll are you doing, Shunpike?" he shouted charging the older man and shoving him away from Nicky before drawing his wand, "what the hell is wrong with you? Leave Nicky alone, Freak!"