I think this is a pretty stupid and un-Christian-like idea. They are essentially saying, "We are gonna start our own little 'Christian' government, and the rest of the U.S. can just go to hell." How's that for "loving your neighbor" and spreading the gospel?
The only case where I would be for leaving the U.S. is if it took away my freedoms so as to force me to do something really sinful. Otherwise I'll stay on the ship try to bail out the water she's taking in and even go down with her if that should eventually be the case.
I don't think this could ever succeed. S.C. certainly wouldn't be allowed to secede from the union even if they got so far as to attempt it. I think the website said they were non-violent, so no need to worry about another civil war.