Because of rage at their own inability to master their destiny, they really want to crush the achievement of others under the guise of fairness and equality.
Yeow! That's probably more closer to the truth than anyone knows!
Well done.
I think for some it's even simpler than that. Some people who feel they've been wronged (whether justified or not) blame the system they live under for what happened. So when someone comes along with a utopian idea of a different system, it thus sounds good to them. The actual nature of the system isn't as important as the fact that it opposes capitalism.
That's why the Communist Party used to recruit heavily among ethnic and religious minorities who had faced discrimination. The recruiters would just tell them lies like "All races are equal in communism" or "There is no anti-semitism in the USSR" and they'd buy it.
Yes! You nailed it. My mother called such behavior "cutting off your nose to spite your face"