But on at least two issues, abortion and gays, Christians and other like-minded religious people do support government mandate to cause everyone's behavior to conform to their beliefs.
Preventing gay marriage is targeting one group of society for fewer Constitutional liberties than is enjoyed by the rest of society. How would Christians react to a law that forbade Christians from marrying, while allowing everyone else to marry?
Regarding abortion, it's very unlikely that as a society we will be able to arrive at a nearly 100% consensus, so the issue must be left to personal conscience and individual authority without government mandate. Even God lays the responsibility for our actions squarely on our own shoulders, not government's.