Well then we agree to disagree, since you evidently believe it is fundamentally right to imprison anyone who was a citizen of said nation, that was part of an political party and every member from baker to smith would be imprisoned because a few guys were rotten.
And considering Aethas prior actions it is very improbable for him to betray the Kirin Tor.
It is morally wrong, but it was necessary, just like the exile of the high elves.