Why would you shut up because the pit boss says no? You are dealt 2 aces and want to split the hand. Who wouldn't want to split that hand!
You seem to be under the mistaken impression that Casinos are there to be fair, or to provide good customer service. They aren't. They are there to take your money, and unless you want to be unceremoniously kicked out on your ass, it's best not to argue with the pit boss.
I would also recommend learning the house rules for games before betting - lots of casinos have odd little rules here and there, that are specifically designed for their advantage.