I don't see what is the deal. Something on his shirt? What is it? From this screen, it looks like a coiled snake? Which is the symbol of Don't Tread on Me? The stars on the flag look off though. I cannot see them well on the tiny photo, but looks like more than 50 there.
it's an old flag, so uber lefties with no knowledge of history will brand it racist because we had slavery back then and some seedy elements today have appropriated it as theirs. So rather than claim back some of these icons (Betsy Ross flag, Gadsden flag) which have for a long time have a historical and patriotic meaning, they relinquish it to the nationalists who fly it alongside the confederate & nazi flags.