I'd argue against killing whoever ided it. If the unided is in a T room where the body can be taken out in an alternate route, then I'd be careful. MC Hotel is a good scenario, T room in the basement. The body can't be taken through the teleporters into different T rooms so its safe to kill whoever Ided the body.
I'm going to have to qualify this, as it would greatly depend on the time frame. If the T room opens, someone runs in and you shoot them, the door closes, and someone IDs the person you just shot. Then, you can conclude that, based on common sense, that person is in the T room and therefore a traitor. However, if a while has passed/you leave the area and you notice the body being ID'd, you can't necessarily kill as its possible the body was moved outside the T room. So: Yes, but not always, you need to be 100% certain.