I'm assuming you're referring to the segregation era with this comment. That's fair, but there are also glaring differences between that society and ours. Do we think that all of those differences can simply be attributed to a few governmental actions?
I don't think segregation would be wholly unpopular in many areas of the country. I think a segregated business, or segregated housing, would do just fine, particularly if the practice were entirely legal.
If someone said "this is a Christian community;" and discriminated against non-Christians, I would think that many Christians, particularly Evangelical Protestants, wouldn't have a problem with that. Even though that works against societal interests.
It's approached from the belief that the government should be as hands-off of business as possible - probably the only "principle" I really agree with Republican party on. I put that in quotes because they're far from consistent when it comes to legislating to this.
But, if government is hands-off when it comes to businesses, then, well, business could effectively do just about anything right? So long as they aren't denying a person's negative rights, their right to life, liberty, property, etc, then, the businesses could do whatever, no? That includes pollute, harass, coerce, disenfranchise, underpay, exploit.. so long as it was a voluntary association, then, it'd be legal, right?
I don't think the government should be able to tell a cake baker who he can and cannot choose to bake a cake for as he's not denying the fundamental right to life, liberty, or the pursuit of happiness in any sort of substantiated way.
See what I mean...
Then how can the government collect said baker's taxes? Upon what ethical grounds does the government have to tax any business if this is the framework in which we choose to operate?