Few things are as dangerous and nasty as selfishness in the guise of 'for the sake of someone else'...
I think I know what you mean. The determination to work for the good of others can be a dreadful and loathsome weapon. They're blinded by self-righteousness, and have no regards for their surroundings. They don't care what happens to others. They justify themselves for pressing forward pursuing their justice, crushing everything in their way...