This is just like why American airport security is so maligned compared to Israeli security -- the idea that "there ought to be a RULE!" is superior to having inteligent, well-trained, properly-equipped people make the calls.
Go ahead and ban everyone who is annoying whiny griefers without care for their feelings.
Don't ban people because their (race/gender/age group) has a lot of annoying whiny griefers.
Go ahead and let soldiers shadow suspicious persons and terminate confirmed attackers with extreme prejudice.
Don't suddenly say "Mam, the boarder must have made a mistake! Your four-year-old daughter's name is on the no-fly list! GET HER OFF THAT PLANE NOW!" (actually happened, more or less) or "I know this urn is sealed and marked HUMAN REMAINS, and the TSA specifically told me not to mess with them, and it passed all the scanners, and the passenger warned me about it before hand. I'm still going to unseal it and stir my finger around in it to look for contraband shampoo/hand sanitizer/baby formula!" (also happened) or "IT HAS BLINKING LEDS AND ISN"T SEALED! ITS A BOMB! <uh, that's my breadboard blinker pendant. do you like it?> (two days later) YOU SHOULD BE ASHAMED OF YOURSELF FOR BRINGING FAKE BOMBS TO AN AIRPORT YOU AMERICA-HATER!" (also happened)
The point is that when "there should be a LAW!" gets in the way of actually getting things done, the forces you are attempting to filter automatically win.
Griefers make admins ban vast swathes of populace = people given grief.
Terrorists make government accuse and aggressively interrogate and demean the populace = people are terrorized.
People who think that banning a section of the populace from your community and hiring thugs to keep the people in line will remove problem individuals are both very patriotic and very deluded.
A proper filtering of undesirables requires personal involvement.
To keep up the airport security parallel, Israel observes the crowds from the moment they enter the airport to single out suspiciously-behaving people, and puts multiple armed soldiers on each flight, some in uniform and some undercover. If someone is suspicious, they move their seat at the last minute to make them sit in the middle of a bunch of soldiers. If nothing happens, they can go at the end of their flight. If they try to attack something, there are a lot of opportunities for the soldiers to knife them, beat them senseless, or; if worst comes to worst, open fire (I presume they are given safety-fragmentation bullets to reduce chances of penetrating the hull or ricocheting).
You already have a proper first screen in that you have to apply to get in. A good second screen would be simply to keep an eye on new players. There is very little someone can do that can't be solved by a look at the logs, a banhammering, and a minute or two of admin work.