If you aren't playing the game by the rules, then their is no game to play.
The concept that players shouldn't expect that they be held to the rules they agreed to play by is just backwards. That adults, or people acting in adult settings, can't handle having a warning issued for mucking up the rules of the game is completely nonsensical. That you conceive being corrected by a TO as some shameful action and a warning as some draconian sanction is just silly. It's just a warning. Are you asserting that repeated rules mistakes shouldn't result in a Game Loss/ DQ? That's just plain non-tenable, so what's the issue with providing clear guidelines for how further issue is going to be resolved by warning the player that there could be future consequences. Now there is no room for any confusion on the players part over how things will be handled and no room for any accusation of impropriety towards the TO if subsequent sanctions are needed.