Man, I like this question! First, let’s look at the dictionary definitions of “moderate.”

1a: avoiding extremes of behavior or expression: observing reasonable limits <a moderate drinker> b : CALM, TEMPERATE
2a: tending toward the mean or average amount or dimension
b: having average or less than average quality : MEDIOCRE
3: professing or characterized by political or social beliefs that are not extreme
4: limited in scope or effect
5: not expensive: reasonable or low in price
6: of a color: of medium lightness and medium chroma

Next, consider “theology.”

1: the study of religious faith, practice, and experience; especially: the study of God and of God's relation to the world
2a: a theological theory or system <Thomist theology> <a theology of atonement>
b: a distinctive body of theological opinion <Catholic theology>
3: a usually 4-year course of specialized religious training in a Roman Catholic major seminary

Going back to the original question, “What is wrong with being a moderate in regards to theology?” I would answer that there is nothing wrong with moderation in regards to the study of religious faith, practice and experience. Nor is there anything wrong with moderation in regards to theological theories, systems or bodies of theological opinion.

However, I would beg to differ in regards to the study of God and God’s relation to the world. I just don’t think you can get enough of that. For Biblical support, I refer you to Psalm 119:

v7 – “I will praise you with an upright heart, when I learn your righteous rules.”
v9-12 – “How can a young man keep his way pure? By guarding it according to your word. With my whole heart I seek you; let me not wander from your commandments! I have stored up your word in my heart, that I might not sin against you. Blessed are you, O LORD; teach me your statutes!”
v14-16 – “In the way of your testimonies I delight as much as in all riches. I will meditate on your precepts and fix my eyes on your ways. I will delight in your statutes; I will not forget your word.”

I could go on and on.

In closing: Is not the Bible one of the greatest ways that God has chosen to reveal Himself to us? We must study Him via dutiful study of His Holy Word!

Thank you for posting this question. I enjoyed responding to it.

With Christ's love,
Ted