Your link was a truncated FB bit. So I went to the site and looked at the article about a guy who wore a Trump hat to a BLM protest that had been organized right after the shooting death of a black man.
Cruc will tell you that he had it coming. Well, if he's consistent. I won't. You should be able to wear the emblem of association with what many in the black community feel is a racist candidate for the presidency. Even at an event where you know passions will be enflamed, given the particular nature/reason for this rally. You should be able to take a vacation to Israel wearing your Arafat t-shirt too. But the chances are if you're doing that you have something other than participating in a peaceful, stress free afternoon.
It's a little like protesters who show up at a Trump rally.
Here's a link to one being physically assaulted. There are more. And you know what both videos prove? Nothing, as far as establishing a rule goes. All they manage to support is the notion that if you are in a provocative stance among "the enemy" of your position and tempers are flaring, someone (likely you) will get hurt.
Anecdotes can be good for illustrating a rule, but they don't establish the rule.