First, I don’t think he can be charged with a crime.
It was a hidden camera conversation and he wasn’t speaking to an audience trying to incite unrest, he was just giving his opinion to one person.
Second, he didn’t say he was going to beat up cops or burn down Milwaukee, just that it would happen, giving his opinion that supporters would be pissed if Bernie is nominated.
I think this is enough evidence for the city of Milwaukee to cancel the DNC convention in their city due to the threats of violence, from those peace loving socialist Democrats. But wait until about one week before the convention before canceling so they have to scramble to find another location.