On hackers: Nobody should constantly make remarks like "yeah, right" or "nice prefire" to any guest or member. Period. I see this all the time coming from our own members and admins and even GS from time to time. It's embarrassing to me as an MFF member when I see that type of remark. That is not the way to handle a suspected cheater.
Non-Admins - if you suspect someone of cheating, ask an admin to come to spec with you. Don't accuse anyone in the server.
Admins: If you suspect someone of cheating or have a member or guest ask you to spec someone that they suspect of cheating - check them out in spec and decide if they are or not. If they are, remove them from the server without all the fanfare (pianos, meteors and such) or return to the server and resume play if they don't seem to be cheating. Get a 2nd or even 3rd opinion if you aren't 95% sure before kicking or banning. If they are disrupting the server in other ways (language, inappropriate name, constant spawnkilling after warning, etc) just kick 'em. If that doesn't get the point across - or if the offense was offensive enough - then ban 'em. It's not that difficult. We want family-friendly, fair players in our servers.