Let 'em. With an adult there to prevent choking, point one against their argument. Point Two: Parents should be able to play with the baby in a manner suitable for the child's age. I find this a perfect father/child bonding experience. Dad teases the kid with the milk, but doesn't prevent him from having it. As great a game as the "Airplane flying into the hanger" one used with solid foods. I hope mom was watching. THAT would make an interesting video if she tried that.