Actually the FOM says I no longer have to wear the hat so I still have the right to not wear it and be a pilot.
You depend on the FOM to tell you how to be a professional? As Rez said, professionals don't need to be policed, and they don't need to be told by an FOM something as basic as how to dress like a pilot. You should police yourself and wear your full uniform with pride. Management has no vested interest in you continuing to look like a professional. They want you to continue to slide deeper into the depths of the blue-collar everyday laborer. You're helping them with your pathetic attitude about your appearance.
Are you saying the ones who choose not to wear the hat when not required are not professional? I thought all airline pilots were professionals. Is it only the ones that chose to play dress-up?
No, not all air line pilots are professionals. Simply holding an ATP cert and a company ID doesn't make you a professional. Professionalism is about attitude. Your attitude is to do the least amount possible to get by. That's not the attitude of a true professional. Just by referring to it as "playing dress-up" demonstrates your unprofessional and immature attitude.