Which conflict, typical in the 1960s and 1970s, does the case Spence v. Washington involve?

Spence hung an american flag upside down with peace symbols on it outside his apartment and was tried for this. An original decision to fine him $75 and give him 10 days in jail was reversed as it was found that he had a right to communicate his message that the US should stand for peace instead of killing people in Cambodia and the Kent 'State University. This type of conflict was common in the '60s and 70's with protestors against the war in Vietnam and the killings of people fighting for black civil rights. Muhammed Ali's refusal to fight in the war against the Vietnamese was another high profile example of this type of protest.