Kailyn Lowry shut down an Instagram hater criticizing her single mom status after her fourth son’s arrival.“Why do y’all do this?” the Teen Mom 2 star, 28, captioned a screenshot of a direct message.The troll wrote, “You’re a f—king single mom with four kids and you’re on TV. … You’re supposed to be stopping pregnancy of the younger generation, yet you went on to have four f—king kids with deadbeat dads that don’t want to be there for you.