[OP of "Would it violate any law to set up a website where people can submit the details (names, license numbers, workplace, addresses) of Bernie supporters and communists they meet IRL into a database?"]

Mind you it would not collect a person's "real official" identity info, but rather the submitters opinion of the existence of such person's... If that's any legal circumvention at all...

Submitters would perhaps need to submit pictures of bumber sticker, person wearing a pin, holding a sign, yard sign, work desk swag or reasonable supporting documentation showing the communist affection, before the profile would be accepted into the database.

This could be a useful tool to discriminate based on political beliefs, for employers. It could be used to shame and entertain, or to keep a running dossier on communists and hold them accountable as they try to backstab their comrades.

Of course I imagine the database would be hosted in a swarm of distributed cloud hosting so it can't be taken down with a simple cease and desist.