I say never because the plausible deniability that the site needs is ruined if we subscribe to the idea of "No calling the cops...but..." If we want to contact any authority, it really has to be mediated through Null. The police raid on Lucas has shown that. It doesn't matter if none of us did it, but now he can accuse KiwiFarms as a whole for getting the cops involved instead of just someone like Josh.
Obviously, he would have still gone and blamed the entire website and false flaggers even more obviously won't go through Josh, but that's just my opinion.