I can take a crack at it based on the Christians I have talked to in real life and than maybe some of the non-Mormons can comment on what I have said. Specific instances of discord I have observed are:
1) Seeing the USA as the new holy land. I don't know, for the record if this perception is correct or not, but non Mormons see the idea of a post-Israel holy land as revolting or blasphemy. Not blasphemy in a way where there needs to be physical retaliation but more along the lines it goes against their interpretation of the KJV and is therefore invalid.
Jesrusalem was destroyed because of the wickedness of the people. Musilims and jews are not chrisitans. why would god continue to promise a land to someone when they reject Christ completely and insist on destroyign themselves?
The U.S.A. is the greatest nation in the world, every other country turns to us for help because we are the only country who has the means to make a difference. the U.N. is on American Soil.
40 years before the Civil War, Joseph Smith prophesied of it in the Doctrine and Covenants. Aside from the wars we have brought on with ourselves (civil war ect...) there have been no battles that ensued on american soil. That was promsed in the Book of Mormon.
2) Protestants reject the idea, by and large, that any of the Bible (aka book of Mormon and book of Abraham) could have been written in the last few hundred years.
3) The idea of a modern prophet feels diminishing towards the 12 prophets who are revered by protestants.
Of course because they think that god will never reveal anything to them beyond christ. If thta is the case, why is there a pope? why are there religious leaders? if they cannot recieve any new revelation what is thier purpose?
4) liberal Christians feel the Bible is the inspired word of God vs the literal and any religion that has literal interpretations would have a diminished validity to many of them.
Why woudl anyoen believe the truth is not plain and simple, why would God want to confuse people? is it not said in the bible that the devil is the father of al lies and confusion?
5) Christians who feel that Christianity doesn't need to be restored (irregardless of reason of why it doesn't) will have issues with a religion that promotes restoration of Christianity.
The Book of Mormon is not "Restoring Christianity" it is restoring the true nature and credentials for salvation, not only of people who are alive now, but also for those who have passed on.
alot of people believe the "Judgement" comes immediately after death. does it not say they in the bible that all mankind will be resurrected? How will mankind be resurrected if they are to burn in hell immediately after death?
6) The idea of a Mormon Satan, who seems to be viewed as an opposing God in Mormonism is a direct contradiction of the fallen angel idea that other Christians take on Satan.
It's actually the exact same as the "fallen angel" We believe Lucifer and Jesus both presented thier plans to Heavenly Father, and when Jesus' plan was selected Lucifer got butthurt and 1/3 of the hosts of heaven left with him when he was cast out. Lucifer and his followers can never attain a physical body and will be miserable forever because we chose to follow god and recieved something he can no loger attain. So, he wants to bring as many of us as he can with him to be cast into "Outer Darkness" after the Judgement.
7) The Mormons feel that the Mormons are "Gods chosen people" whereas many Christians feel that the Jews are "God's chosen people" creating a mutually exclusive paradigm between the two ideas.
The Jews are Christ's chosen people. Unfortunately they rejected him, so there was a need for another people to build his kingdom. We believe when he appears again, he will appear to the Jews first. And then sit at the throne of his Kingdom on Earth (The Kingdom the Latter-day Saints are building) to reign during the Millenium.