My boss is a Baptist from Brazil (4th generation Baptist, not a recent convert). One day we were talking about theology and the subject of Santification/Justification came up. He stated "Well, Lutherans and Catholics believe the same thing in that regard". I went to great lengths to outline the differences (in our eyes I guess), and he looked at me and said "Well, isn't that the same?"
Through the centuries, we have become a lot closer in that regard. So close that many of the Reformed confessions no longer see Lutherans as part of the Reformation (Not on this site, but others I lurk at).
I assume you mean that LCMS is viewed that way by the reformed churches. With all the denominations out there, you can see why non-Lutherans would expect other non-LCMS Lutheran denominations to be similarly conservative in their doctrine, but boy is that wrong. Although I stick closely to the LCMS doctrine, I also prefer to try to find the similarities and commonalities that bind Christians together with us, and not for those things that separate us. Perhaps that comes from spending so much time overseas where I was the “outsider” and where I felt Christians need to stick together for strength. Here in the US we live in sort of a cocoon of religious freedom and diversity, which allows us the “luxury” of nitpicking. If history teaches us anything, it is that the Christian Church has usually grown stronger through persecution and weakened/apostatized during times of plenty. With what I see going on with radical Islam in Europe, for example, I wonder whether Christianity is going to be tested severely again. I don’t know if Europe is up to the task however...are we? (different topic).