Might be too broad. Especially as the scale gets smaller I think that non-quantitative aspects can reasonably affect who you want to do business with. For example, if I'm annoying and rude to my local mechanic and he starts charging me extra to deal with my bullshit I don't really see a problem with that.

There does start to be a problem however if he's the only mechanic in town or if he charges more or less based on race or some other protected class.

I think it's a very hard in general to find the balance on problems like this one, and I don't expect you can come up with a one size fits all rule.