All of my local orgs are social clubs for well off middle class white kids who basically act like twitter ultras in real life. If one of them took a massive socdem turn I wouldn’t be surprised, but I also wouldn’t think they were infiltrated. Sometimes political groups just have poor political instincts, no government infiltration needed.

And it’s a self-selecting process too. Any group that is kind of terrible and incompetent won’t have competent people want to join, so they just kind of dig themselves deeper into their own incompetence.