Shady

However, rulings like this will encourage protesters to arm themselves.

At that time police forces were ordered to stay away from and not police the events. Hence the vigilantism. 

The left has a conveniently bad memory.

Riots are also vigilantism.  Regardless, everyone shot tried to physically attack Rittenhouse. One told him he was going to kill him and chased after him while somebody else fired a gun shot over his head while he was running away.  And you wonder why he thought his life was in danger?  Are you serious?  The other hit him in the head with a skateboard from behind.  The one with a gun pointed it at him before getting shot.  Give your head a shake and actually look at the facts of the case.