I partially agree with OP on this one. Admins, whether they're the host of the server or just a lowly admin, shouldn't ban users unless they break a rule on the server, and from what i've read, OP hasn't broken any server rules or really done anything that warrants a ban.
As for the other opinions, i can see how one can get irritating if that person complains too much, or is annoying in general. Even so, banning someone permanently because you think they are a troll seems to be more of an excuse to ban someone if you ask me, especially if they haven't done anything that warrants a ban. That and leaving the ban reason blank is really lazy, even a one word reason would've sufficed.