Nothing... I read the tweet as a stray shot at the 'authoritarian left'.

He does it all the time.
I asked you specifically about his first tweet not his second tweet with the video, and you agreed with his first tweet
So Kaep #TakeAKnee protest was concocted by the 'Authoritarian' left so ultimately people will bow down to them forever?
Do you see what Rubin is trying to do here?, I know there are libertarians out there who support Kaep and are passionate against police brutality and support criminal justice reform.
Rubin is cleary trying to dissuade these people from supporting Kaep by turning his protest into a partisan issue about the evil left.