Although many people on the left in general don't like to admit it, I do believe that some radical actions can be counterproductive to your cause, especially if your cause depends on convincing people from other sides of the political spectrum. This is valid for environmentalist or LGBT acceptance etc you need to get more people on board, not to repel the moderates.

That said, the difficulty is to find the right balance. And some radical action by fringe groups can help moderates to be more easily accepted by the mainstream. I would expect environmentalism to be now so ingrained in mainstream politics in Europe that some more radical actions wouldn't jeopardize the main cause.

But, far-right politics is going up everywhere in the continent and they're eager to profit from some small radical actions. We're still very far from any form of "ecoterrorism" but we already see them echoing the word.. European elections next year will be crucial, the risk of the EU giving a sharp turn right, with the EPP siding with the far-right is real. And that would be a catastrophe for our environment.