One of the great moral puzzles of the twentieth and twenty-first century

Prager asks why the left (communism and socialism, he means) does not wear the label of evil that they have so rightly earned.

Stated simply, it's because the left are the ones doing the labeling.

Then he asks if you can name anyone on the left who has lost credibility because of something they said?

There are a few. Generally whenever someone on the left says something horrible, all that is requested of them is that they apologize. Usually when they apologize, they throw in a few "you blockheads misunderstood my wonderful intentions or misinterpreted my innocent words"-type accusations and then all is well, because now it is clearly demonstrated that it's the right wing's evil core that is to blame in the issue.

But let a right-winger misspeak, and we get out the tar and feathers.