I'm reminded of a prior employer who didn't want us doing nontrivial networking at our desks, so they used STP traffic as a sort of canary. If you plugged in a switch that was smart enough to be running STP, your port would be disabled for 30 minutes.

So of course, we puzzled it out with wireshark, disabled STP, and created a monster by running network cables over the cube partitions. Sometime later we accidentally brought the network to its knees with the fallout of a switching loop (which is what STP prevents).

As a policy, it was like if you needed to pass a breathalyzer in order to put on your seatbelt.

A better approach is friendliness, and gently pointing out how dangerous it is. "Hey man - careful with those kids. My neighbor died that way growing up - might be worth pulling them into the cab" is more likely to get a "Really? Dang, yea, you're right"