Do you think it's possible for someone to think that owning a slave was wrong, but not for the state to make it illegal?
Yes. It's not an admirable position, nor would I agree with it, but it is a position one can hold. In fact, it was held by a large number of otherwise respectable people prior to the civil war.
Absolutely not!
Do you think it's possible for someone to think that murder is wrong, but to stand against government's duty to enforce ancient, God given laws against it?
The government exists, if for nothing else, to protect life and liberty. If the government can not or will not protect life and liberty or refuses to administer justice against those who violate life and liberty, then that State has violated it's ordination and risks imminent judgment from God.