Standing on top of the winch is considered griefing, but it does not warrant a ban for someone, at least for the first offence. Yes, you can "just" kill the person on the winch, but it is griefing for the simple reason that you are blocking something that should not be blocked by a single person. The most i would do when i actually see someone on the servers doing it, is a warning and maybe a kick if he does it again. Only repeated offenders would get a ban in that case, because it is a grey area in the rules.
But since Rhekimos hasn't been warned for this i will leave it at a warning for now. Do NOT camp on the winch again. Either kill the person or jump on it for a second to interrupt the animation, it's not really fair game, but it's something no admin will ever do anything about. But standing on it for a couple of minutes to block it is not okay.
(It's not in the rules, so "common sense" applies here)
Also, let the "OMG FIPS IS SO BIASED" bullshit commence!