Rights are complicated things and we already have rights to speech and association enshrined in the Constitution. The liberty to practice religion without discrimination is in there too, (though without the explicit backing of the government). People can already privately discriminate against those whose marriages (or lifestyles) they dislike, and without government interference. To further enshrine in law a right to use the teachings, of a particular religious group, as an excuse to discriminate against other Americans is not only against the spirit of a free and open society but would be to explicitly show governmental preference for that particular religion (and the beliefs that arise from it), in this case through federal funding. Imposing such a law would weaken the legitimacy of religious freedom through forcing taxpayers to fund the bigotry of others.