There’s a time for everything, and cracking jokes about your kids in he middle of an address to the world about another horrible terrorist attack is probably not the right time. If someone Obama loved was killed in a brutal terrorist attack, would he still be cracking jokes?
On another note, if Obama spent half as much time trying to think of ways to make America more safe as he does attempting to convince the world Muslims have nothing to do with Islamic terrorists, we would all be feeling a bit more safe.