May be once he would have fought dirty. But this was a different time. So he used other means to fight an opponent without a wand. "You know Weasley, you are wasting your life. Your wasting away the chance everyone who died lost. I don’t care you hate me, but if you keep baiting me, I will respond. Believe me if I wanted you dead, you would be and no one would even know how. And you can hide behind Potter if that bothers you,’ saying that he turned to leave. Then as if he remembered something he turned back and said, "Don’t insult Granger. At least she is doing something rather than moping around. She is making a difference. She is still fighting for a cause. She is fighting for friendship, for life while you are running away from your own family and hiding in here. You’ll never be half the person she is.’