I support the aims of Extinction Rebellion, and took part in one of their actions against the Silvertown Tunnel. This was at the Blackwall roundabout - a notorious deathtrap for cyclists. I did find problems with the ER tactics - not that the sliproad was blocked periodically, but that it was blocked at the access point for the local bus route.
5 buses were held up for nearly an hour, and many passengers were not impressed. The reason given by the organisers for obstructing the buses as well as the main road was that protesters would otherwise have had to form the timed blockades by walking along a narrow verge, which was more dangerous than a wider section of pavement. I thought this was unfortunate, all things considered. If ambulances were obstructed I wouldn't have taken part.
Insulate Britain have a far weaker case. Their demands are superficial. I don't know if they take chances with their own safety, but their campaign would seem to be concerned with energy, so they should target energy interests to be effective. I therefore wonder if their organisers can be entirely sincere.
I also wonder this about the anti-vaxx protests that target hospitals.