It's called To Catch a Predator. I believe it started as a little segment on Dateline NBC, then turned into its own show thing for a bit. Or maybe it was always a standalone thing, I can't recall.
Anyway, the premise is that they get someone to pretend to be an underage girl online, then find people who want to come have sex with them. It's a sort of documentary and report on sexual predators who use internet chatrooms to find young girls to fuck. They worked with police to get these people in, film them coming in as you saw, and then the host Chris Hansen comes out and talks to them about their creeper status. Then they try to leave and the cops nab them.
It's actually pretty fucking hilarious, these guys say some stupid shit. For example:
It's creepy, but it's also amusing as fuck. :D