Llamamoe parent
You have a point but we are literally talking about an association whose entire and only raison d'etre is to perpetuate violent crime. Maybe it shouldn't be outright criminal, since people can potentially register for other reasons than to participate, but it definitely should at least be under scrutiny.
I don’t mean to defend people joining groups committing any kind of violence, but this is the kind of rhetoric being used by the far-right against their opponents, not only in the US; it is a terrible idea to allow policing based on “assumed intent”.
It's the same direction of travel as recent UK laws allowing police to stop people preparing to join protests if they think the accused might be planning to e.g. glue themselves to something.
IMO this is basically policing thought crimes. It worries me.
Rhetoric can be used to justify any action against any group on very arbitrary pretenses, and while I don't think "groups whose primary reason for existing is explicitly to facilitate crime should be closely scrutinized" is particularly dystopian, you're probably right that it could provide a good starting point for a slippery slope of criminalising association with political opposition :/