...Is that it's so enthusiastically backed by people who seem entirely incapable of recognizing the possibility that they may do evil in its name.
"We're defending the downtrodden"? "We're defending those who have been unjustly persecuted"? Great talk. It's the same shit that was said by the Stalinists, the Maoists, the Nazis and just about every other monster to walk the earth.
"But we're different! They were evil - we're not!" Once again, great. They said the same thing about all their opponents too.
Of course, the cynic in me believes that at least the smarter SJWs know this, and simply don't care. This is just the latest viable path to power. If the path changes, so will their tone. Hell, so will their stated beliefs. The desire for power and control? That will generally be staying in place.