First, if you only allow christians into your public[1] restaurant that would be illegal. But no one would come because they found out you were an ass and the government would take you to court for violating the Civil rights act.

Second, you are in your rights to do those things. You can't discriminate based on race, age, gender or religion; tats, piercings and ugliness are fair game.

If you are in the US, CA or EU you should read up on what the local human rights/civil rights laws entail.

Edit: There are exemptions for "members only" places, which is different than public restaurants. but then you would no longer be a restaurant but considered a club. For example, the gym, curves, is members only. One of the membership requirements is being a woman. If they decide to open a coffeeshop on the side they wouldn't be allowed to have it open to the public. It's either fully open or mostly closed, now in between.

"Second, you are in your rights to do those things. You can't discriminate based on race, age, gender or religion; tats, piercings and ugliness are fair game."

Really, when you think about it, not being a christian is a choice (which is why I didn't mention race, age, or gender). Just like this guy being an asshole.

It's not much different. Someone is getting excluded from business because another group doesn't like them.

While I think that anyone should be allowed to discriminate against anyone they want to in private forums (i.e. restaurants or businesses), laws prevent you from discriminating on the basis of sex although not appearance (with the exception of a few states) or if the position is covered under the Bona Fide Occupational Qualification exception. That being said, "being an asshole" isn't a covered category under anti-discrimination law, so they're perfectly allowed to discriminate all they want.

Irascible human being is not fit for PR/Marketing. Whether he's a christian or has earrings does not come into factor.

Its called judging a man by the content of his character and/or skills. Its not discrimination. Someone with Parkinson's is unfit for a bomb disposal unit. Someone with arts degree is useless as Rocket scientist and useless at a NASA convention.

rolling..rolling.rolling..my free speech is gone.

You get what you pay for.

Having ill-considered opinions down voted isn't a violation of your right to free speech (which was never guaranteed in a private venue in the first place, by the by).

Instead, it's an expression of everyone else's speech. You're allowed to be wrong. Others are allowed to point it out.