The people being affected aren't going to stop and think "wow, you're right, capitalism is killing the environment, I need to become a marxist". They're gonna think "I wish the police would come throw these bozos in jail (and maybe beat them up first to discourage others)". I would love to see any reasonable study indicating that blocking traffic has any positive outcomes.
It seems to me like nonviolent terrorism, e.g. "we're gonna deprive you of your rights until you support our political cause".