I'd boycott Applebees for this except... I never eat there anyway because a random TV Dinner from the grocery store is better quality and taste and I don't have to go sit in a poorly controlled environment to do so.
I agree the guy was a jerk, but it should be common sense for any employee that they can't expect to keep their job after revealing private customer information, publicly humiliating that customer, and in this case very likely damaging that customer's career. Duh?
(Incidentally, I'm apparently not the only one who got that detail wrong, since the original post on Reddit was titled "My mistake sir...")