This is naive. There are an infinite number of ways to legally discriminate. Not all discrimination is bad. When you buy a five star product over a one star product you are discriminating.
When you're SELLING a five star product, and you choose only to SELL it to [people who you look upon favorably] then you're discriminating.
Someone looks at one star homes (for example) on AirBnB, and five star. Chooses a five star. They haven't discriminated against any protected class in choosing the five star home. The homeowner absolutely can by refusing.