So far they said you can't be arrested just warned. The only consequence may be the store not letting you shop there.
Then do not go into the store. They have the legal right to establish their own rules even if you do not agree with them or think they are based upon faulty info. That's the business's decision. You either adhere to their policy, or don't go in. Simple.
As for the rest of the conspiracy theory ... ugh. Dude! It's a potentially debilitating disease (and NOT a simple "flu" as you seem to think). How virulent it is or is not may be up to debate, but it's there. And paraphrasing one researcher at Stanford, "The only thing we know for certain about this virus is how much we do not know." So, it is better to be safe than sorry. If you're not going to be safe, maybe you need to stay inside.