Actually, the point of his message is keep our violence on our own planet. If it spills out into space, we will be visited by the space police (like Gort) and we will not like (or survive) the visit.

I haven't looked at the other posts yet, so I'm throwing my solution in before I go reading. Turn on the first switch. Wait a while. Turn off the first switch. Turn on the second switch. Go upstairs. If the light is on, it's the second switch. If the light off, feel the bulb. If it's hot, it's the first switch, otherwise it's the third switch.