"Benevolent" = "wanting to do good". But that applied (I think) even to the Communists. They wanted to free the proletariat from oppression. That was their moral imperative. To do it, they were willing to execute their "oppressors". The temptation to have mercy on some of the oppressors rather than execute them had to be resisted, because it would hinder the cause.

[Edit: reworded for clarity.]