Were they blocking searches with warrants or warrantless raids? And was what they did illegal? I read the article but left unclear on both of these key questions.
If they had simply kicked off users who were likely cops, that would have been legal. That’s what (some) biker bars do.
But they went beyond that and actively misled such users in a way that wasted their time. That amounts to lying to investigators and is illegal.
You can kick people out of your bar for giving off a cop vibe. You can’t keep them around and feed them fake intel on drug deals so they waste their time.
You can pull your shade down to keep people from looking in your window. You can’t make shadow puppets of a homicide with the intent to get the cop outside to investigate a spurious lead.
Any relevant case law on this? Lying to the police isn't allowed, but lying to some new guy at the bar is legal, regardless of your suspicions of who the new guy is.
Believing that you're merely lying to "the new guy" or "an abusive user" isn't enough, as you note, so that part of the program (send spurious data to likely bots) wasn't illegal.