I agree, but how does arguing about contraception help any of us who are already in right-standing with God? This issue isn't pivotal because it isn't about others coming to Christ.Because marriage is a holy commitment; a vocation. It's not something that two people simply do because it's nice.
Of course it's pivotal. It's a subject of telling God "God, you're welcome in OUR marriage, but when we go to bed, you'll have to take a hike." We don't stop being Christians in the bedroom. Our Christian duty continues in every single activity.
The idea that certain sins can be taken or left is damning.