I have the joy of flying every week for work and have found out that almost everything is up to the discretion of the TSA people. Some airports allow some things and not other airports. It also depends on the time of day, the crowd, the TSA person, the phase of the moon etc. And there is no point in ever arguing with them. That just makes the situation worse and you can never win.
That being said, you can't go wrong with putting it in your 311 bag (i even carry extra bags for clueless travelers around me).
These rules continually evolve and change on a regular basis and it's hard to keep up.