you know what it means to 'reverse' your emotions?
I think what your doctor means is that you find the emotions you are experiencing so overwhelming that you are effectively white-washing them with different 'easier' emotions.

So rather than feeling say debilitating helplessness or fear etc you feel anger, something you and a lot of people find easier to deal with, even though it is not in itself pleasant(though it may be in ways).

Your doctor doesn't care about it, because it's just a distraction, a red-herring and is not your real problem, if you become able to deal with your real problem, and then learn to deal with your feelings in a more positive way, chances are these feelings will vanish, and you will even wonder, if you really were the same person who thought about violence and revenge.