Dalebert, I think you're misunderstanding employment law.
The business only is prohibited from discriminating against a religious person -- like they can't say "I won't hire you because you're X".
See the EEOC -->
http://www.eeoc.gov/laws/types/religion.cfmWorkplaces are required to make reasonable accomodations unless it's unduly burdensome. So, if the religious person is driving away customers, costing the company business, they don't need to hire them or keep them on staff. (edit to add:
http://www.eeoc.gov/eeoc/publications/backlash-employee.cfm says you can't fire someone just because their religion makes customers uncomfortable, however I do recall a case when I was studying Employment Law that stated if it's a bit more than just the mere religion that's the issue, you can fire them. I believe in the case I read, an anti-abortion Christian woman would wear buttons on her clothes that showed very very graphic photos of fetuses being aborted, but she claimed she had to wear them as part of her religious duties to discourage abortions. Her co-workers were very disturbed, getting sick even because of it, and the court said it was okay to fire her. So, perhaps in your scenario it'd be problemsome if you were starting the conversations with customers about Satanism instead of them just asking questions, and if no reasonable accommodation could be made, like having you work in the back during busy hours, etc.)
The only thing I see troublesome about your proposal (if I am understanding it right) to get rid of all protections and just let people fend for themselves is that the freedom to contract isn't really a reality. It might work bargaining with a small company, but if someone wants to work at like. . .McDonald's or some other huge place, all the contracts are going to be standard boilerplate doctrines. If there's no religious/spiritual protections at all, I don't see why these giant corps. would bother making any reasonable accomodations (for religious/spiritual folks, as well as other protected classes). It's cheaper and easier to have everyone the same -- everyone look the same, everyone of the same physical/mental abilities, etc. Anyone who's "different" would have to get a job with a company or small business only run by people of the same faith or those who are accepting.
Yeah, sometimes it does suck for businesses if customers are afraid of a particular person. But, we still enforced Equal Protection after segregation was ended. It would be totally unreasonable to say "it's okay restaurant to not hire black servers because it would scare the white folks". Sure, some people nowadays get afraid when they see someone in hijab, a turban, with a Satanic necklace, etc. There's a line between it being an unreasonable accommodation and one that is being abused simply for discrimatory reasons.
--------------
BTW, I've also read the Satanic Bible by LaVey and I really enjoy the philosophy. When I was Pagan, I was greatly influenced by his theories.(And, he does have a great sense of humor which everyone needs

)