I think the best way of going after US flag desecration is to bring a flag likely beloved by the desecraters, and desecrate it as well.
For example, the rainbow flag. Communist flags. The Palestinian flag. Others:
http://st2.depositphotos.com/4600785/7206/v/950/depositphotos_72067381-LGBT-symbols-and-flags.jpg
Agree. I think stomping on a “Che” flag would be most effective.