And before common law, aspects of governance included the Magna Carta, the Nordic "Thing" (town meeting, legislature) and other writings on morality, rule of law, etc.
IOW civil laws which agree with religious views, merely strengthens both.
Take a different subject, sex with minors. Religious views, and civil laws both oppose it.
Claiming the rule is because of or derived from religion, does not lessen the validity of it.
The point here is that the people get to choose their own laws regardless of the basis.
If Wyoming wants to outlaw cattle rustling, they should be allowed to do so without regard to whether that decision is religion-based.
If Oregon wants to set up their own state-run health insurance program, they should be allowed to regardless of basis.
If Vermont wants to allow same-sex marriage, then they should be allowed to do so.
And if California wants to define marrage as between one man and one woman, they likewise should be allowed to do so without regard of whether that decision is religion-based.
Liberals on the other hand don't believe any of this. They believe that states should only be allowed to do what they want them to do. And if they choose to do otherwise, then the power of the courts should be used against them to force them to adopt laws contrary to their own will, but fully in line with what liberals want.
In short, liberals are tyrants who have no qualms about using the point of a government gun to get what they want.
Sure, they issue emotional arguments of why things must be that way or why you are some religious neanderthal bigot for holding a view contrary to theirs. But when the question comes down to who gets to decide what the law is, they always grow silent knowing that they alone should be the ones to call the shots.