In this regard, The Washington Post characterizes the view of anti-marriage-equality pastors thus:
But Thomas and the 77 other Baptist ministers in the association do not see same-sex marriage as a civil rights matter. Rather, they say, it is a question of Scripture, of whether a country based on Judeo-Christian principles will honor what’s written in Romans or decide to make secular decisions about what’s right.Apart from the seriously question-begging reference to "a country based on Judeo-Christian principles," I agree completely with this framing of the issue, and under the First Amendment, the answer should be clear.
Enlightened self-interest should lead the pastors to the same conclusion. Do they seriously want the government to be the final arbiter of the correct interpretation of "what's written in Romans" or any other part of the Bible? What would they do if the government granted itself that authority and then took a position directly contradictory to theirs?