I just watched a Journey Home episode on EWTN with a former LDS elder. He said there were a couple things that really opened his eyes that the Mormon church was not the true Church. One of the biggest things was the teaching that God was once a man and has evolved to a god. It never sat well with him (with good reason!) Jesus, as you may know, is not viewed as God but rather the Son of God but a separate God. He too is considered a man who evolved into a god. But a Catholic priest asked this man to read Hebrews 13:8 "8: Jesus Christ is the same yesterday and today and for ever. " and it really struck him that the whole Mormon theology of evolving was unscriptural.
Interesting that the very first temptation from Satan in the Garden of Eden was that eating of the fruit would make man as gods…
This man said that many Mormons do not know about the core teachings of the Church, such as evolution to godhood nor do they know about the secret temple practices. Many Mormons suspect there are some real theological problems but they love the fellowship so much that they basically turn a blind eye. They are also taught to flee if someone really nails them on the scriptural unsoundness of the LDS church, so be prepared for that.
I would also like to add that in the Gospel of John, Jesus tells the woman at the well who says she knows the Messiah is coming, " I, who speak to you, am he." John 4:26 Now, cross-reference that with Isaiah 9:6 messianic prophecy " 6: For to us a child is born, to us a son is given; and the government will be upon his shoulder, and his name will be called “Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace.”
There is a lot more but I’m tired and I have to get the kids to bed. I will try to post more in the morning.