Why do people have to compare body counts of communist and fascist systems. Yes, I know many if not most people underestimate/do not know the "cost" in lives of

Why do people have to compare body counts of communist and fascist systems. Yes, I know many if not most people underestimate/do not know the "cost" in lives of Soviet and Chinese communism, but it just seems... wrong to compare how many more millions each one killed than the other. --- One death is a tragedy, a million is a statistic. (Sorry for butchering the quote)