That's... kind of the whole point, Leo. Like him or not, Seymour shines in that moment because we not only learn of his ulterior motives (less support the troops in the eradication of Sin and more laugh as the lambs line up for the slaughter) and confirm Tidus's suspicions that he's up to no good all in one.
It's hardly one of the worst moments left btw. You're straight up wrong about that one. The worst are the ones the troublemakers are gathering around, but you cant really do much about that without increasing the saves.
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Bunny... :3
http://img.imgcake.com/baronvontoast/0413121622bjpguh.jpg