They need to hear the Gospel proclaimed in all its fulness, Geer. As a former Lutheran, I can say with certainty that they love Christ, but they have a warped notion of the nature of His sacrifice, the nature of the Church, and the nature of Grace, one that is clearly incompatible with the teachings of Sacred Scripture and the Fathers of the Church.
At first glance, a lot of people wonder why we should bother reaching out to Lutherans: Afterall, many elements of Lutheran worship closely resemble the Novus Ordo/Divine Liturgy of St John Chrysostom, but this does not mean that they possess the fullness of faith by any means. There’s no Eucharist. No valid sacraments save for marriage and baptism, and the Lutherans only consider the latter to be a sacrament (the Lutheran church has even abandoned the teachings of Luther and his closest followers!). I often hear many Lutherans and Catholics alike saying “we’re so close in belief anyway. Why bother converting in either direction?” It boggles my mind.
Yes, Lutherans are indeed Christians, but they are outside of the fullness of the faith, many of them through no fault of their own. They need to hear the Gospel preached with authority and in its proper context, not some narrow-minded protestant interpretation.