The Baptist objection to saying “God damn it” is not that the speaker is saying God should be damned. The objection is to taking the Lord’s name in vain, which is based on the Old Testament prohibition on uttering God’s name. It doesn’t make a lot of sense to me — “God” isn’t God’s name (the Tetragrammaton is) — but I suppose it is based on a view that the translation of the Tetragrammaton into English is “God.” For the same reason, Baptists won’t say “Jesus Christ!” when they hit their thumb with a hammer.
As I learned it, the Old Testament prohibition is based on a view that stating someone’s name gives the speaker of dominion and control over the person referred to, which is why Adam got to name all of the animals in the creation myth. If you speak the name of God, according to this view, you conjure him and thereby assert some measure of dominion and control over him, which was a no-no for the ancient Israelites.
He can correct me if I’m wrong, but I believe the prohibition on uttering the name of God is the reason Strickland33 writes “G-d” instead of “God.”