Religious extremism and violence is something that has plagued humanity all throughout history. All religions (and all worldviews for that matter) have been used throughout history to justify some pretty heinous actions. Christians are not immune to spiritual blind spots. Christians have used the Bible to justify crusades, slavery, and segregation.
Of course, there were Christians against each of these injustices, but there were many who defended these actions. It's easy for us to look back and say, "what were they thinking?" However, what blind spots are hindering us that we may not see right now? And how can we avoid these blind spots (as best we can)? Here's the start of a list that may help. Of course this list is not exhaustive and I do not have the space to fully explain each, but this is a start. Let me know what you think.
1. Your beliefs should produce a deeper love for God and others.
As Christians, if our faith is making us more angry or bitter or mean, we may want to question who we're really following. The fruits of the spirit are "love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self control."
2. Your beliefs should be consistent with the main themes of scripture. (love, mercy, redemption, holiness)
No doctrine should be based on a single passage of scripture. Less clear passages should be interpreted by clearer passages. The Old Testament should be interpreted in light of the New. As Christians, our faith should include the major themes like grace, redemption, and holiness because they permeate throughout the whole Bible.
3. Your beliefs should be consistent with the life and teachings of Jesus Christ. He is our final and complete revelation of God.
Jesus is the complete and full picture of God (see Hebrews 1). Thus, our theology should begin and end (and default) to Jesus. Love this quote...
"The historic Christine doctrine of the divinity of Christ does not simply mean that Jesus is like God. It is far more radical than that. It means God is like Jesus. In other words, the doctrines of the incarnation and deity of Christ are meant to tell us that we cannot start with a predetermined, set-in-stone idea of God derived from the rest of the Bible (or philosophy) and then extend that to Jesus. Jesus is not intended merely to fit into those predetermined categories; he is intended to explode them, transform them, alter them forever, and bring us to a new evolutionary level in our understanding of God. An old definition of God does not define Jesus-the experience of God in Jesus requires a brand-new definition or understanding of God." –Elton Trueblood
4.Your beliefs should NOT major on the minors and minor on the majors.
The Pharisees had the habit of doing this and it seemed to bug Jesus (see Matthew 23). This doesn't mean the "minors" are unimportant...just don't miss the "majors" in the process. Stuff like justice, mercy, and faith.
5. Your beliefs should NOT force the Bible to answer questions it wasn't asking and your beliefs should NOT confuse Biblical truth with cultural preferences.
Do not look for Bible verses to prove your predetermined belief. This is called proof-texting and it always leads to trouble. If we're not careful, we can "make" the Bible say (or justify) anything we want. Also, we often confuse being a Christian for being republican (conservative) or democrat (liberal) or traditional or hippy. This will quickly skew our ability to understand and apply scripture. I'm not saying we should be apolitical, but never let it be your first allegiance.
6. Your beliefs should have conviction but always open to deeper understanding.
The Pharisees are a classic example of individuals who held so strongly to their beliefs that they were not open to a new understanding of how God's kingdom works. They missed the messiah standing right in front of them. Often are own cultural bias and fears can keep us from learning and growing.
7. Your beliefs should produce a deeper love for God and others.
I know this is number one as well. I'm being redundant on purpose. As followers of Christ, our faith should always lead to love for God and love for others. These are the two most important commands. If we miss this, we miss everything.