The problem is that the specific argument you point to is often brought up either in complete ignorance or straight up bad faith. Communism bad, look at (insert one of like, 5 events here)

But let’s ignore the untold millions slaughtered, enslaved, or maimed in the name of profit.

The problem with your argument is that it can be applied to anything.

“This specific argument is often brought up either in complete ignorance or straight up bad faith. Nazism bad, look at (insert one of like, 5 events here)”

I could even sprinkle that turd with: “It wasn’t Real National Socialsm! Actual National Socialsm has never been tried!”