"the guy wasn't too bright to walk into the middle of an angry demonstration and disagree"

This is inaccurate.

There is no disagreeing with them until they start abusing him.

The guy is at pains to point out that noone there knows what he thinks or ever asked him what his opinion was.

His only utterances are on the subject of the aggression he received.

The only thing they've got to criticize him for are being black, having a hat, and being there.