My thoughts are that you’re a free citizen and what you do in your spare time and how you groom yourself are absolutely none of his business. That said, in all states, employment is at-will, which means he can fire you for no reason, so if he gets petty about this, he could fire you and because the reasoning wouldn’t violate any discrimination laws, he’d be within his legal rights and you’d have no recourse. Personally, I find this level of control completely unacceptable. Employers have the right to control us at work, when they’re paying for the privilege. I’d be willing to die on that hill rather than let an employer try to dictate how and where I am to have my hair done.