The relationship of many American leftists to patriotism reminds me a lot of those guys who grow up in oppressively evangelical communities and decide to express their disillusionment with it by becoming black metal satanists - a oppositional mirror of Christianity - instead of becoming atheists.
Like the correct response to the realization that nationalism is a false consciousness used to suppress class conflict is to focus on raising class consciousness not to root against the nation everyone around you is rooting for.
Flag burning anti-patriotism is stupid in the exact same way that jingoistic chauvinism is stupid but it's also stupid in an additional self-defeating way because it sets your goals up in opposition to a bunch of symbols and institutions that normies have been trained their whole life to believe in.
I see your point, but I am not sure that flag burning in the late 60's was stupid and self defeating. I think they got good framework for first amendment rights out of a court so.eqhat receptive and moved the overton window.