I'm going to assume that you're rather young.
That said, flying a flag in a country that is not yours, USED TO BE, back when we were still (semi-)sane, was deemed an act of war.
You know not of what you speak. I am willing to defend the American flag by use of force, but I am still not willing to burn a Mexican flag.
And it is only an act of war if the government of Mexico raised the flag. Otherwise I could get Spain to declare war on France with only the cost of airfare and a French flag.