Are you asking why any pastor would turn down a chance to perform a wedding which is contrary to biblical beliefs? I don’t understand your statement.
“contrary to biblical beliefs”
You are on shaky Theological grounds. Remarrying divorced people is prohibited by Jesus because they are committing adultery. We aren’t exactly obeying those Biblical beliefs now.
Romans 13 instructs us to obey the government authorities (Note: I didn’t write Romans so don’t blame me for what it says). So pastors have to follow the law. But the law doesn’t instruct them regarding what they must say. If they want to use Romans 1, have at it.
Note : I did not write this.
Rom 13:1-5
(1) Let every soul be subject unto the higher powers. For there is no power but of God: the powers that be are ordained of God.
(2) Whosoever therefore resisteth the power, resisteth the ordinance of God: and they that resist shall receive to themselves damnation.
(3) For rulers are not a terror to good works, but to the evil. Wilt thou then not be afraid of the power? do that which is good, and thou shalt have praise of the same:
(4) For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil.
(5) Wherefore ye must needs be subject, not only for wrath, but also for conscience sake.