But it was a joke. You're blowing the prank way out of proportion. This would have been a simple, harmless prank call if there wasn't a mentally ill person in the equation and we wouldn't even be having this discussion.
There's a strong historic precedent for comedians approaching ordinary people and making them look foolish for the sake of comedy. Triumph the Insult Dog, Crank Yankers, Steve Penk, Jay Walking, Sgt. Hartman, Jerky Boys, Guido Hatzis, Mark Knopfler, Dave and Rupert Annoy People, Joe Pesci, You kick my dog, is Mr Wall there, is your fridge running?
Watching ordinary people floundering for the sake of comedy can be extremely funny when done properly and there's no need to start a witch-hunt just because one mentally ill person had an illogically suicidal reaction to a phone call.