"The reasons that the Mormons and JW are shunned by other Christians is that it is this key belief on who God is and what salvation is and how it is acheived that is distorted. "
It's interesting that you use the word "shunned." I've always wondered why any Christian would "shun" anyone. That, to me, seems like a real denial of the core of Christianity.
Perhaps you meant something else, and just used the wrong word.
Is it a denial of the core of the internal combustion engine to cool it with water?
This is where the concept comes...
NIV 1 Corinthians 5:11-13
11. But now I am writing you that you must not associate with anyone who calls himself a brother but is sexually immoral or greedy, an idolater or a slanderer, a drunkard or a swindler. With such a man do not even eat.
12. What business is it of mine to judge those outside the church? Are you not to judge those inside?
13. God will judge those outside. "Expel the wicked man from among you."
Probably the polygamy of the early LDS organization fit them into the 'sexually immoral' label. Perhaps the 'idolatry' would fit on the strange concept of the Christ.
We don't shun Mormons and JW in the sense that we cease to be friendly with them or share the true gospel with them. But we do shun them in the sense that we formally declare Mormon and JW belief as non-Christian.