Can I be fired for wearing something the boss does not like?

I want to start by promoting a discussion about employment at-will in the United States.

Employment at-will is a concept I had a hard time with in my 20s. I now see that it is a vital characteristic of a successful society. If your boss hates the color blue and you wear a blue shirt, you can be fired. You might think this is insanity - but you have the same rights. If you think his red shirt is nasty, you can march right up to him and quit.

Employment at-will is the mechanism that self regulates your salary. You present an employer your skills and merits and they decide how much they are worth. If you have enough of these things you will not be fired because you are valuable and finding valuable people is hard. If you are not compensated enough it is your will to find more profitable employment.

There seems to be some strange idea that employers are members of some sort of elite patriarchy and the people they hire are expendable lemmings that do the same work. The opposite if usually the case - Employers look for people that have the characteristics they need to make the organization profit. Profit is not an evil thing, it is needed to keep the cash flowing to all employees.

Employment at-will is a great thing. One should not confuse this with being fired or not hired for discrimination of immutable characteristics like skin color or sex. There are laws in the USA that forbid this.