Legal Question in Business Law in Minnesota

The sale of goods is a voluntary contract, and as such a business can choose to enter into or not enter into the contract.

Unless the goods are "public accomodations" such as restaurant food, etc. you can determine with whom you wish to do business.

Usually yes, but there can be things that change the general rule. For example, your contracts could dictate odd terms to you. Or there could possibly be anti-trust issues. Of course, even if you are legally correct, a frivolous lawsuit wouldn't be shocking.