IF a traitor causes an rdm fest by shooting one person (person A) who perceives the shooter to be person B and then kills person B because B was behind A, can B rightfully report A and A be slain?
Yes, they can report them and be slain. The shooter may have caused it, but Person A killed person B based on their location.
That would be a yes, and no, depending on the response from player A for killing player B. As in, Player A has full right to kill player B in your scenario as he was not doing anything when player C shot him. This usually happens during a big battle in cramped spots on some maps; not all the players know the terminology that seriousTTT uses, but they get the idea of it. However, if this is looked with black and white folds, player A would be slain without any inspections as the only response he gave was that he believed that player B had shot, which he had not. Shooting wrong people would be considered RDM.