I thought that  the Civil Rights Movement answered the question: Can a business that does business with the public discriminate against anyone?
If the answer is YES, then any business that wants to can find reasons to discriminate against anyone for whatever reason they choose.
If the answer is NO, then the business has to serve all that come in for their product.
If the conservative religious want to make this an issue of religious freedom, then they should have to answer if the Si Ins were WRONG, because they challenged the religious faith of the store owners.