Do you condemn the Christian crusades from the Middle Ages? How about the Christian crusade going on right now? There is a crusade against gays. Will you stand up and denounce such hatred as having nothing to do with Jesus or His Church?
When it comes to the issue of gay marriage, the church must stop asking the state to protect the sanctity of marriage. This is idolatry. In this excellent article by David Dunn, he shows us that the church has no business asking the state to help us define and defend our sacraments. This is making the state into a false god.
CS Lewis never wrote about gay marriage (as far as I know) but his comments on governments making laws about divorce are applicable to the issue. If anything has been learned from history, we know that it is bad for everybody when any religion picks up the sword of government and tries to enforce religious laws on anybody.
The only way to truly teach grace is to engage in living grace among other people. How are you living grace in your own life? In this post I share a few principles I try to follow as I live out grace among other people.