Even the Hell’s Angels would not put up with that...................
But suppose they burned a rainbow flag along with it.
What do you mean EVEN the Hell’s Angels? Despite their whatever criminal/gang activities they may be involved in they are rabidly [sometimes even viciously] patriotic.
If the HA had been at that “flag burning”, it is very likely the flag burners would have received a heck of a lot more than a few “slaps”. It would probably have gotten VERY ugly.
Have you not read/heard about of their exploits at anti-war rallies during the sixties?