What is your ethical obligation to thwart angle shooters?

[tipperdog]

I've been playing Party SnG steps lately, and have found a surprisingly common angle-shot. Basically, when you're on the bubble (e.g. with four people left when three advance), the shooter will chat some variation of: Congratulations! We all move ahead now! I've seen this several times, and I'm sure the shooters aren't making honest mistakes--they're attempting to induce some victim to push all in to end the tourney (STEPs usually end with random all-ins, since the software doesn't halt the tourney when the threshhold to advance is reached).

What (if anything) would you do if confronted with such an angle-shooter?