Marx? that's just historic ignorance. Stalin maybe. Now, you have to be very careful with that statement. Superficial statements as "Many communist organizations and communist leaders were known for their antisemitism" can be as well stated about religion, blacks, whites, children,... What originally is an economic contradiction is taken as something else, just because it is convenient as anti-communist propaganda. And you know very well how propaganda works. It is a misinterpretation in many cases of what is originally a communism-capitalism problem to be stated as a communism-religious group contradiction. If a religious group (an Jews, Catholics, Muslims,... serve the same as examples) stand in anticommunists stances then, of course, they will get reaction from the communists. The rest is just propaganda, ignorance and opportunistic intentions.