Interesting point of view, never thought about the irish liberation, even though it was a recent development.

My opinion is that the fear of marxism permeating the civil right movement (especially the BPP) and starting to reach the Latino and disfavored white people (the "rainbow movement" if i remember correctly) did strike fear into the US government (hence the assassination of Fred Hampton, who really started this). This fear allowed to Civil right movement to be successful, because ethnic tension, while useful to exploit a minority, is not worth the danger to the social order.