JOEL - While it is true that we believe that exaltation can come only through living the doctrine and ordinances of the LDS church, members have always been counceled to not take the "we're right and you are wrong" attitude when interacting with members of other faiths. We should be humbled in the fact that we have made serious promises to God to live up to certain laws and covenants, which makes it highly likely that we could end up in a lower place in heaven than non-members would if we do not endure. In fact this is probably the case with many members of the LDS church. We must also consider that the heaven Christians of other faiths will go to, if they live their religion, will be everything and more than what they expect it to be, even though it is not exaltation. We should never say never(well almost never). God is a fair, just and loving God. If they deserve exaltation He will find a way to make sure they have every chance to obtain it; if not in this life then in the next.

Consider what Boyd K. Packer said:
"One doctrine presents a particular challenge. It is our firm conviction that The Church of Jesus Christ of Latter-day Saints is, as the revelations state, “the only true and living church upon the face of the whole earth.” (D&C 1:30.)
This doctrine often generates resistance and repels the casual investigator.
Some have said, “We want nothing to do with anyone who makes so presumptuous a claim as that.”
The early Latter-day Saints were bitterly persecuted for holding to this doctrine. They were the butt of many clever stories. We, of course, are not free from that today.
Should we not then make one accommodation and set this doctrine aside? Would it not be better to have more accept what would be left of the gospel than the relatively few who are converted now?
Some have recommended that we confine ourselves strictly to evidences of the gospel: happy family life, and temperate living, and so on. Could we not use the words better or best? The word "only" really isn’t the most appealing way to begin a discussion of the gospel. If we thought only in terms of diplomacy or popularity, surely we should change our course.
But we must hold tightly to it even though some turn away.
It is little wonder that our missionaries are sometimes thought to be overbearing, even when they are most courteous.
If our main desire is to be accepted and approved, surely we will feel uncomfortable when others reject the gospel.
We know there are decent, respectable, humble people in many churches, Christian and otherwise. In turn, sadly enough, there are so-called Latter-day Saints who by comparison are not as worthy, for they do not keep their covenants.
But it is not a matter of comparing individuals. We are not baptized collectively, nor will we be judged collectively.
Good conduct without the ordinances of the gospel will neither redeem nor exalt mankind; covenants and the ordinances are essential. We are required to teach the doctrines, even the unpopular ones." (“The Only True Church,” Ensign, Nov. 1985, 80)