You can't stop it. Laws are a blunt instrument that imposes the will of the majority on the minority, which is something the Constitution (the supreme law of the US) is supposed to protect individuals against.
Rights are inalienable. All people are supposed to be treated equally as described in the Constitution. Special "rights" for individuals of any color or belief, if created by the Federal government, are unconstitutional. Individual rights cannot be taken away, but they can be ignored, trod upon or violated.
If a law had a large financial penalty attached to it, I'm betting the store owner would simply provide a reason that seemed more "reasonable". I doubt they'd blatantly voice an opinion that could land them in trouble with the law. Laws cannot eliminate discriminatory beliefs. I personally would refuse to do business with an establishment that openly discriminates against people, but that's me.
I like Cook, but at the risk of being the contrarian here I think he should keep the focus 100% on Apple and on the products. Anything unrelated to Apple is a distraction and not his job to fix. If he wants to be a political activist, he should make that his focus.
There is a historical component to Mormon church "approved" racism. I recall Mormons at one point believed (perhaps they still do believe) that black people came from mud. Any Mormons here might want to speak to this.
I'm not sure that's completely fair. Look at it this way, if a person is prejudiced against another person for any reason (the reason may be rational or irrational) a law cannot force that person to be any less prejudiced. Do you agree? I see plenty of emotionally wrought and irrational arguments against people of all colors and beliefs by people of all colors and opposing beliefs.
How would any person prove material harm from Google's actions? All that is provable is that Google violated Apple's security features and possible local laws? The likely outcome is a large monetary extraction from Google that will go right into the coffers of the government, to the benefit of no one but the government.