Resentment.

Resentment can be transformed into a governing emotion and a social cause, and thereby gain release from the constraints that normally contain it. This happens when resentment loses the specificity of its target, and becomes directed to society as a whole. That, it seems to me, is what happens when left-wing movements take over. In such cases resentment ceases to be a response to another’s unmerited success and becomes instead an existential posture: the posture of the one whom the world has betrayed. Such a person does not seek to negotiate within existing structures, but to gain total power, so as to abolish the structures themselves. He will set himself against all forms of mediation, compromise and debate, and against the legal and moral norms that give a voice to the dissenter and sovereignty to the ordinary person. He will set about destroying the enemy, whom he will conceive in collective terms, as the class, group or race that hitherto controlled the world and which must now in turn be controlled. And all institutions that grant protection to that class or a voice in the political process will be targets for his destructive rage. That posture is, in my view, the core of a serious social disorder.

Sir Roger Scruton, from Fools, Frauds and Firebrands: Thinkers of the New Left