When American's engage in illegal wars in far off countries and kill millions in the name of "freedom and democracy", there is little any person of conscience can do except throw themselves upon the gears of the military-industrial-congressional-complex.
The Weather Underground weren't truly violent, they avoided killing and bombed property, places the government used to continue unjust causes. Apparently the only people who died were their own soldiers. They could easily have hit hospitals, and schools, or stadiums full of republicans like Nixon, but they deemed the killing of unaware innocents to be wrong. I'm surprised they were not all hunted down and killed for such anti-american thinking. The fact that they were not, demonstrates the underlying incompetence of our American 'security' forces.
The use of terrorism, the killing of those not directly engaged in killing others is unforgivable, it is what American Soldiers do best, and in this Weatherman Underground case would have been hypocritical. But in the case of American Wars, I see no injustice in "An Eye for An Eye". If Iraq or Afghanistan had the ability to drop bombs from drones on American Cities and kill groups at funerals or weddings, they would be justified. Just a the Vietnamese would be justified in killing about two million Americans, due to the unjust and unnecessary war we perpetrated on them for 25 years.
Seeing the results of Agent Orange on their population, and the birth defects of Iraqi children due to Depleted Uranium and other toxic chemicals released by the American wars, if I were them it would be difficult for me to forgive the invading army. I think those who choose to forget or forgive us do so out of survival instinct, because they would have to effectively commit suicide attacking the dominant force or go mad in frustration. This is why these wars don't make the U.S. more secure, they just increase our insecurity because they motivate untold numbers of future fighters who can justify anything, even actual violence as a means of just retribution.
In my opinion the Wether Underground were heros, they helped raise political awareness in the USA and probably defused Vietnamese vengeance. To such a war torn country as Vietnam, the project of attacking civilians half-way around the world would seem worse than useless if that country were already tearing themselves apart from the inside with civilian resistance.
America is not a great country, we are deeply flawed. Our strength lies in the founding principals and values of our Constitution, yet even it has had to be Amended 27 times. And back in the 1960's Americans were even more openly bigoted and racist, willing to destroy nations without any public dialog. I guess not much different than today. Where are the students in the Universities today? Where are the survivors of Kent State? Where are the protests and sit-ins, where is the underground? Guess it's not hard to tell which way the wind blows.