They're looking for those violent responses, since they think that will cause the public to become sympathetic to their cause. 

Here's a snippet of an article about Extinction Rebellion Belgium (posting  just a snippet since the full article is behind a paywall) . I know they're talking specifically about police violence, but I assume they're just looking for any sort of violent response. 

Screenshot: https://imgur.com/i8VP9Iu

I'm not a big fan of these radical people, even though I do believe human caused climate change is 100% real. Taking them off the metro was right IMO, but kicking them while they're down is not. Although I can understand the frustration.