Oh, are you sure about that?

Do you REALLY think I'd be so stupid as to entrust a kill switch to some random bloke?

I'll just push your robot down the pit, as I know you won't dare run the disc... that lexan really won't help you too much against a 50 megaton explosion, you know :P

Oh, and if a hypothetical kill switch did exist... well, antimatter doesn't go off on a small scale like you say, it's all or nothing emphasis being on the all.