The following was my response to him:
Yes, the Book of Mormon presents some things differently than the modern LDS Church practices and the Bible teaches.
I don't mean that flippantly - and I don't mean to make light of what you've said to me. It's just that nothing about our theology and ideology even comes close to implying that nothing should have changed from then to now (either from 600BC-400AD to now, if someone accepts the literal timing claims of the Book of Mormon, or from 1829-2011, if someone doesn't). Sure, there's a "same organization" mentality - but even that can't be totally accurate when we look at an evolving organization.
If you look at what was taught in the Old Testament and how it is different than what is taught in the New Testament, for example, you can reach either of the following extreme conclusions quite easily:
1) The New Testament is crap! It contradicts the Old Testament.
2) The Old Testament is crap! It is contradicted by the New Testament.
I prefer the following conclusion, personally:
It's neat to see how different people viewed God differently - and how those differences influenced their teachings and organizations. It gives me more options and possibilities as I try to figure out what makes the most sense to me, personally. I'm glad I have such competing, sometimes conflicting accounts and perspectives - since, if we accept all of them as "scripture", it allows me to find my own way and not think it has to be exactly like someone else's.
For me, that beats, "It's crap!" every time.