The devil wants you in hell. He wants to destroy you. That is his whole mission in life. He stalks about like a roaring lion seeking whom he may devour.
The devil doesn’t care about abortion, or gay marriage, or evolution. Believing in the Biblical teaching on any of those doctrines will not save you. He only cares about one thing- the cross of Christ. Only faith in the cross can save you. So the devil uses all those other things to open up chinks in the Christian’s trust in the Bible so that he can attack the one thing he really cares about.
That’s why everything the Bible says, including what it says about abortion, gay marriage or evolution matters- all of those things exist inside the wall of the infallibility of Scripture. If you let the enemy inside your wall because he promises he won’t steal your greatest treasure, but only some smaller things that you think are unimportant, don’t complain when he doesn’t stop with those things. If you let the thief in your house when he promises only to steal a little money, you have only yourself to blame when he steals it all.
Don’t let the devil inside your house. Don’t believe that he will stop with abortion, or gay marriage, or evolution, any more than Hitler stopped with the Sudetenland. He’s after the whole kit and caboodle and he won’t stop until he gets it. Defend the wall at every point, even and especially where it’s most seriously attacked. Defend the authority of Scripture on every point regardless of how unpopular it is. Because regardless of what you think is at stake, the same thing is always at stake when it comes to the authority of Scripture- the cross of Christ, and your soul.