Reading the comments on this topic, i have come to the conclusion that the people on this board give tennessee way too much credit for being loud, and are really really glad they are getting to talk about something other than how bad the state of tennessee football is....
Far worse decisions are being made by people everyday than taking your child to a football game of any magnitude. Taking an 8 week old, 8 month old, 18 month old, 8 year old, 18 year old to a football game is a decision to be made by that parent and what their expectations are for the game. The OP was simply surprised by though of having to purchase another ticket not whether or not everyone thought it was the right thing to do.
Some of you act like he will be taking this baby to a war zone, when, in all reality, there will be tons of empty sections where he can sit safely and watch the game.
And chances are, they won't stop you for another ticket if you are wearing your child. Just hand them the tickets you have and you should be good.