[Frumanchu]

It stems primarily from a inability to distinguish national, ethnic Israel from spiritual Israel (hint - only one is truly God's people).

[Buggman]

Wrong. Both are God's people--national Israel is the root and the natural branches, and we Gentiles are grafted into that root by God's grace. Your theology is equivalent to saying that because I have an adopted brother, I am no longer my parents' firstborn.

And if some of the branches were broken off, and you, being a wild olive tree, were grafted in among them, and became a sharer of the root and the fatness of the olive tree with them, do not boast against the branches. But if you boast, it is not you that bears the root, but the root bears you. You will say then, The branches were broken off so that I might be grafted in. Well, because of unbelief they were broken off, and you stand by faith. Do not be high-minded, but fear. For if God did not spare the natural branches, fear lest He also may not spare you either!
--Rom. 11:17-21

If God has not preserved national Israel, the natural branches, then there is no such thing as "Preservation of the Saints." You can't have it both ways.