What's with the obsession for hats??? Why even make an issue out of it? Many airlines do have hats as part of the uniform, but don't make a big fuss about wearing them. If you like it you can wear it and if you don't like it you don't wear it. As someone pointed out the hat can be of some use in an emergency for crowd control purposes, so having it in your bag just in case is not a big effort...
As far as everyday work goes, hats is NOT what makes a pilot professional. I would even claim that the ones who make the hat a big issue are the ones who have lost themselves on a sidetrack and don't remember what the job is all about. Complaining about a colleague not wearing a hat is not professional. There should be more important things to think about. And if there are not - well then it's a sad thing for the whole profession.
Not wearing a hat is not what reduces the respect for our profession. Making it a big issue is.