Oh. No, I meant the strip, not the activists. The implication is that we're all so dumb that we end up underwater but we're still complaining about how the activists were assholes. For the joke to work, the stunt itself needs to be pointless. If the stunt was indeed to "provoke action against climate change" the strip would make no sense. The premise of the joke requires the action it's defending to be useless.
So yeah, to me this transmits that a) the author thinks the action itself did not work and was not going to work in the first place, and b) the author thinks we're getting angry about it instead of taking action against climate change because we're dumb and we don't get it, so the action was fine, it's our fault.
It's the children who are wrong, but also we're entirely powerless, but it's because everybody is stupid except for us, only the activism is to make everybody else stop being stupid only it can't work becasue of how stupid you all are. Impotence and Skinner-esque arrogance for a tasty mix of surreal kafkaesque self-contradiction.