Because he was an identifiable culprit. There is still quite a difference between "not secret" and "public".
I fail to see what it changes. He just needs to join up for 1 second to get access to the list and note it down. Then the damage is done. It's not as if I could ban the members of certain realms to join the faith to begin with, knowing who did it doesn't bring me anything. It's obviously someone from a realm waging a crusade against the faith, so he's immune to any kind of reprisal.
No better than had people been able to publicly see this data though some new feature. Indeed, at least this way it wouldn't feel like a blatant violation of fair play.
