Do you believe that every single action one must do be perfectly in line with leftist ideas to be a leftist? Is it not possible to commit evil for the purposes of, in their minds, securing the chances for achieving Socialism and Communism?
Stalin, by and large, was a leftist that was dedicated to the cause of achieving Communism. He was also a cruel, evil brute, who cared little for the Means of achieving it.
I prefer to recognize evil leftists to learn from them and their mistakes so as not to repeat them.