FWIW, I am LCMS and totally believe the official doctrine of the LCMS, however, one of the most famous LCMS legislators was that liberal, Paul Simon. I have NOTHING in common with him except our membership was at the same church but he deserved to be excommunicated just like the wack job liberals who call themselves Catholics. They're no more Catholic than Paul Simon was LCMS.
No argument there, but I do think it’s possible for a faithful protestant to believe that he has Catholic brothers and sisters in Christ. A church should exist for what it believes, not in opposition to those who it rejects.