When the Vietnam war started to become unpopular, it was unthinkable for most to be critical of the government during a war.  It was considered unpatriotic.  Then, as the casualities mounted and an atrocity was exposed-more people came out against the war.  Then it became ignorant, close-minded, or stupid to be for the war.

This created a paradigm for fools, wherein any pro-American or patriotic expression was considered stupid and any antagonist of the USA was automatically given the liberal rubber stamp of approval.  This is why the left is enamored with communism-because it is antithetical to America and the Constitution. This is why the left reveres every religion except Christianity-because America was and still is largely a Christian nation.  This is why tolerance is the highest ideal when considering the Ground Zero Mosque, while Christians are not allowed to pray in public.

This attitude of the left has caused the exact condition they accused supporters of the war back in the '70s-ignorance.