Your post is irrelevant. Political thought is not protected.  Not serving a cop may be disgusting, but it can be chalked up to political reasons. Legal. No shirt and shoes? That is a health issue. Who does it discriminate against? Everyone, not just one group or person. You want to bring firearms into this?

If you own a business you have the right to refuse entry to people carrying a firearm. That is your right. 
I own many firearms and completely agree with property owner’s right to not allow firearms on their property.

You have faild massively in understanding this issue. All of the forms of “discrimination” you mentioned are legal. Refusing to serve a gay in Colorado is illegal. See how that works?