On July 4, 1776 we essentially burned the flag of the gov't then oppressing us. Our nation's "father" urged the new nation to make no alliances with foreign princes and despots, & yet that's been official U.S. policy for generations. We openly support and defend one of the most oppressive regimes on Earth, the Saudi family dictatorship, which regularly slaughters its own people and neighbors with weapons we sold them. July 4th is an appropriate day to declare our own independence from such heinous policies, & some people choose to express their desire to be free of complicity with such evil by burning its symbol. 
How do you show your disdain for our gov't's murderous, anti-freedom foreign policy? Why do you support our overthrow of democracy, e.g. Chile, Guatemala, & Iran? Those who bray about their love for freedom but support the Saudis are hypocrites. 
http://www.foxnews.com/us/2017/09/09/saudi-government-allegedly-funded-dry-run-for-911-report-says.html