Everyone can play the game of saying everything horrific in the past or today is directly attributable to the economic system that they oppose and that their opponents advocate, and we can even go further and play tricks like this: "Nazism was really a left-wing system in nature". See, it's great fun.
Ultimately it's pointless though; it doesn't persuade anyone to think differently about anything, and serves only to make the writer feel righteous, without needing to go to the effort of formulating and advocating something genuinely better and workable for the future.
And as far as death tolls, they're completely indefensible, that's why I am not a proponent of communism or other anti-democratic ideologies. But it is curious that the death tolls from fascism never get added to the death toll of capitalism. Each ideological wing generates human suffering at the far end of anti-democracy, which is what we need to avoid, whether it comes disguised as facism or communism, or whatever else.
Conflating the two is part of the propaganda we've been sold for nearly a century now.