So there used to be a convention in Japan for folks who loved Shota and Cub comics, called ShotaCon. I can't seem to find any mention of it anymore. Does anyone know if it still exists and if so where? Is there anything similar out there?

I think it's called NAMBLA now

I thought that show was called How to Catch a Predator?

You're probably looking for Shotaket.
Shotacon is the name of the genre, just like lolicon. ...and no, I have no idea why I actually know that. Never been into that stuff.

If something similar were even remotely allowed here, the place would probably be teeming with party vans.

The word you are looking for is therapy, or prison.

Hoooooow aboooout no