A religious argument is never a pretty thing. Mix politics and religious disagreement and you get something like the 30 Years War, but religious argument alone can be quite nasty. But sometimes these arguments need to be had - the faith needs to be defended. And in these discussions, Scripture is the weapon we use - sharper than any two edged sword.
But how do we use Scripture? Pastor Peters gives an excellent account of the dangers of proof-texting", which is what happens when one just tosses Scriptures out willy-nilly - out of context, to prove a specific point. Scripture is not a grab bag though, it is one unified whole - we don't just throw a verse out and say, "There." We don't use Scripture just as proof for our arguments - that's not the approach we should take.
Rather, we should speak in such a way that what we say flows from Scripture - where Scripture is not only the end, but also the beginning of what we say. As Lutherans, we don't have proof-texts, we have "Sedes Doctrinae" - or "Seats of Doctrine" - verses upon which doctrine rests. And so when we discuss a specific doctrine, we don't just run right to a specific verse and say, "Ah ha! I win!" Rather, we look at what the Scriptures say, and then shape our words from there.
An example of this approach would be infant Baptism. We don't look for the magic bullet verse that says, "Go baptized kiddos" - but rather, we look at the verses that establish what we teach about Baptism and seek to apply them. We are taught in Mark 16 that Baptism is part of the life of salvation (He that believes and is baptized shall be saved) -- we hear in 1 Peter 3 that "Baptism now saves you." Thus, we say that Baptism is part and parcel of salvation. Then we consider what Scripture says about sin - Romans saying that "All have sinned and fall short of the glory of God", or David confessing that "in sin my mother bore me," and from verses like these we see that Scripture teaches that all people, including infants, are sinful and in need of salvation. We consider Matthew 28, that children would be included in "all nations" - or Acts where Peter says that the promise is for "you and your children" on Pentecost - or the whole households being baptized in Acts. To the objection that infants can't really believe, and therefore have no need of baptism (or no benefit), we point to where Paul says that God has made foolish the wisdom of the world (for see, faith is not about human wisdom), or in Ephesians where we see that the faith by which we receive grace is a gift - not a working of our own, not even a working of our mind.
Doctrine is built upon the Scriptures - discussions of God's truth pull from all over His Word -- they are not ended by simply pointing to one passage all by its lonesome and saying, "Hey, there you go." We study the Scriptures - see the picture they paint, and then we speak -- our words that we say are to flow from what we see in Scripture.