If you look at the laws regarding stealing there is an element to it that says" With intent to permanently deprive the lawful owner." I have said before that TSA does not steal anything in regards to items like the pie that we are talking about. You as the passenger have choices.
1. Take it back to your car
2. Give it to someone that is not traveling with you.
3. Send it somewhere by mail ETC.
4. Surrender it at the checkpoint. IE voluntarily abandon it. In which case TSA disposes of it.

Granted all of these cannot apply in all the cases. In most cases the passenger has severly limited their own options because of time or the item that they have is not able to be handled in the prescribed methods because of the consistency of it ( as in the pie.)