I think that argument is pretty weak. Many of the millions that the Soviets sent to the gulags were socialists and communists, but that action doesn't make the Soviets or those they imprisoned and murdered not-communist or not-socialist.
Communists and socialists have a long histories of bloody internecine conflicts.
You'd have to be somewhat detached from the historical record to seriously suggest that all of these, or even a majority, were the result of socialism.
Communists and socialists have a long histories of bloody internecine conflicts.