Wow. That's quite a confession. So a Christian baker shouldn't be allowed to fire a worker who is found to out be a politically active gay who publicly brags about working at a Christian bakery? Sorry, but I disagree. Private business owners, IMO, have a right to hire and fire whom they please.
Maybe I did not write that in a way that makes sense to you. As an employer and owner of a business I can fire your ass for any cause within the limits of the law. That means I can fire or let you go even if I simply just don't like your manners or looks. I do not have to call you a "******* queer" to do that. I can just say you irritate me. Employment is "at will" because people do get to make choices where they work. They are not supposed to be forced to work for anyone.
A business owner owns the business so IMO, they should be allowed to set the terms of their business and who they will do work for. Personally over the years they have been a lot of things I won't do for others for various reasons whatever they may be. I learned early on I did not like working for people I suspected of being assholes. That is why I went to work for myself and ran my own businesses. In today's business climate if I was subjected to the whims of those whom I wouldn't hire previously or do work for I would simply find a way to avoid the conflict or hassle of dealing with them by doing something else. The dude or dudette in your photo most likely wouldn't stand a chance of getting onto the payroll where I signed the checks and made the approvals of hires. I do not care for beards would be adequate enough to turn him away at the door.