People who never expect to be in power can preach and pout and posture and whine. They never have to take grownup responsibility for results, for getting the job done. Leftists who chattered about 'turning it over to the UN' or 'treating it as a crime, not war' obviously do not care at all about actually achieving the result of protecting America.
For several years now, voices on the Left have argued that cultural leftism is a dead end cause and what they should do is to use antiglobalism to win back the white working class voters they lost in the cultural wars. Opposition to globalism falls along class lines, with blue collar voters who have seen their socioeconomic status plummet since 1972, being the most hostile. Blue collar voters, however, are culturally conservative and deeply patriotic and therefore alienated by the left. So some leftists, hoping to reverse the disastrous "Hippies vs Hardhats" rift that tore apart the New Deal coalition wish to get rid of the general infantilism of the Far Left. It comes down to those on the left who get off on being dissidents forever and those who want to seriously rebuild a mass base.