Watch Sarah Silverman’s comments on the 3,000 people who died on 9/11. She calls the Firefighters retarded children for not believing the conspiracy theories concerning the attack on the WTC. That is the real meaning of the joke.
Urban Dictionary
To set your house or business on fire on purpose to get the insurance money.
“Hey, what happened to the bar?”
“The owner wasn’t doing so well so it got struck by Jewish Lightning.”