So it sounds like the people in attendance who challenged it live were aware of it beforehand and showed up to call him out? The linked Twitter post saying "Sad to see such charlatans given a stage at Black Hat" was on August 2nd.

Edit: and a paper critiquing the math was published July 2019: https://unprovable.github.io/drafts/Prime_Generation_For_Bre...

I didn't watch the talk, but if it is anything like the paper many people would be able to call bullshit on the spot, especially those who would attend such a talk in the first place.

Surely the best thing to do with charlatans is put them in the spotlight and expose them. If you refuse to "give them the limelight" then you're just letting them hide their deception long enough to rip [more] people off.