In my opinion, they are a massive problem in that they have successfully poisoned the fans' relationship towards their team.
They have shaped and are constantly driving home the narrative that this United team is morally failing rather than just not performing quite well enough. I think it's on the whole a wrong, bitter, and fateful narrative and looking at a lot of the posts in this place too many fans have taken to it.
The club needs spokespeople pushing back, problem is the only person who ever speaks is the manager.