Public accommodation laws clearly state that a person cannot be discriminated against because of race religion or sexual orientation.
If you want to run a business you have to obey the law.
However any law that is contradictory to the United States Constitution is itself illegal. The United States Constitution provides for the Freedom of Religion and the 'exercise thereof'.
If these people, as NYC pointed out, were discriminating due to color -which is not supported biblically, then there would be a case. In this case, religious teachings and faith/beliefs are supported biblically.
All laws, including all 'general applicable laws', must be weighed against Constitutionality. Again, in a case including race, gender - issues not supported Biblically - one would have a case if declaring 'discrimination', but in this case homosexuality is part of a religious, biblically based faith, and therefore should fall under religious protection.
IF YOU BELIEVE otherwise I completely understand and respect your opinion, as it is still perfectly ok to agree to disagree.