Freedom for me, but not for thee
There are many in the Christian religious right in this nation who complain when they think their religious freedom is infringed, even while they dismiss similar issues from those of other religions, and sometimes erect every impediment they can against Muslims practicing their religion. It’s completely unsurprising that this bias shows up in surveys.
The Constitution requires that all religions are treated the same under the law. Every time you are offended that your religion seems mistreated in law, you should ask yourself how you would evaluate the situation if the shoe were on the other foot. What if a county clerk denied you a marriage license because your fiance were ex-Muslim, and the clerk belongs to a Muslim sect that believes apostates cannot marry? Would you hold up that clerk’s religious freedom to abstain from her secular job? If not, then don’t support a Christian clerk’s refusal to issue marriage licenses to gays. You’re not interested in religious freedom, just in special privilege for your religious beliefs.
One can argue where the lines should be drawn. But they must be drawn the same for all religions. Not just all Christian sects. Not just traditional religions. All religions. One advantage the ACLU has in its defense of religious liberty is that it takes that principle seriously, working for the same rules for Christians, Muslims, Jews, Hindus, Scientologists, Pastafarians, and Sikhs. Many on the religious right, of course, think the ACLU is biased against Christians, because of that. They are so accustomed to special treatment that equality is a large step down.