It's simple, if you suspect him to be faking you, come up with solid proof next time. If he comes in the server more, simply do /players, look at his ID, then do /stats ID (so for example, /stats 4) and you'll see his aliases. Screenshot that.. Imo, making a thread like this with only proof of someone in spectator with a ping timeout is kind of dumb.
Edit, just saw this thread was severely bumped. Excuse me.