Like with this pizza instance, there is a big difference between a gay person entering the restaurant and them refusing to make them pizza vs them asking them to drive to, attend, and cater their wedding.
No, there really isn't. The business provides a service. They do that as part of a social contract in the form of a permit, by accepting money, providing goods and services in exchange for that money and paying taxes and accepting the protections and services that the taxes EVERYONE pays for, roads, power service, water, police and fire, etc.
Why do you think the business should have the benefits of government services that people pay for so the business can make money and then turn away people that paid for the very things the business relies on to stay running?