I guess I remember the days that all U.S. Citizens followed the U.S. Code that states:
"all other persons present should face the flag and stand at attention with their right hand over the heart, and men not in uniform, if applicable, should remove their headdress with their right hand and hold it at the left shoulder, the hand being over the heart"
I guess times have changed, but I always follow the code. If others don't that's their own decision. Personally, I believe that since he was representing Carnival, he should have followed the code as a U.S. Citizen.