Your idea is good.
Let's take it one step farther: the police should put out messages to the "communities" where this nonsense is evident and let the inhabitants know that they, the police, will no longer waste time in those areas where they are not welcome.
Let the idiots stew in their own perversity.
The cops already don't enter those neigborhoods unless they have to.
The shirts mean the thugs have won...and they know it.