I have mixed feelings. On one hand....when we bicker and parse things, the world sees it. And it was Jesus who said "by this will all men know you are my disciples - the lone you have for one another." So I think many of the things we fuss over are just...dumb. Nonessential. Petty.
However, there is so much that calls itself Christianity that isn't. Like you, I believe in the whole of the Bible. I admit it is very hard for me to sit on my hands when someone declares the opposite of God's Word. And I have a few friends who do it in an attempt to not hurt anyone's feelings....not realizing that by ignoring the truth, they are actually enabling someone's destruction.
It's hard. I John 5:11-12 tell us exactly what makes someone a Christian. But I am on the fence about the idea of secondary theology. I think it's because I have heard the whole "Jesus didn't say anything about X" one too many times. Actually, He DID say something about X because He and the Father are One and He is The Word.
But I do agree that authentic Christians need to be unified under the Great Commission and not feud about sprinkling vs immersing, KJV vs NIV, and whether that glass of wine is the worst thing on earth.