it wasn't even going into the bank, it was just near it.
You dug into it. Stop trying to cover it up, just admit it.
Stealing isn't griefing. If someone stole all the stuff and then left, it's griefing. If they stole it and made their own house, it's raiding for your own good.
But why ban him? You could evict him from the city and make him live alone or something.
Notice Oasis said it was a civilized world, it was controlled, there were rules, and If you wanted to be a thief, you had to register as one. Everyone got along except for Thomas, so I sense it's his fault, not ours. If he didn't like the rules, he simply could have left.
The bank had adminium in it. However, Thomas exploited it and found out you can break it by using a lighter on it. Therefore he was exploting a glitch about adminium. Asking him to stop 5 times didn't help. It's a legit ban that no one can argue with. Rules are rules, don't like 'em, gtfo.