This kind of idolatrous (Bible-worshipping) Christianity is indeed offensive—not just to sinners, though, but to thinkers. If you’re not supposed to think for yourself because that would betray a hubristic desire to be godlike, what’s the point of preaching the gospel? To whom is your preaching directed? If God arbitrarily saves whomever he wants to save, what’s the point of trying to convince people to be Christians?
If the saved folks are supposed to be God’s slaves, just as pottery is at the mercy of the potter (Rom. 9:20-21), this conception of Christianity is quite antithetical to American values of liberty and of secular progress. So that’s another reason why it would offend modern individuals who prefer to think of themselves as being free and capable of doing good in the world by their own power.
Yet another reason for being disgusted by this kind of Christianity is the hypocrisy it engenders, as white Evangelicals preach it while still pretending to be patriotic Americans, failing to see the contradiction. It’s the hypocrisy that rankles.