What is dangerous about extremists is not that they are extreme, but they are intolerant. The evil is not in what they say about their cause, but what they say about their opponents.
I am a fan of the writing of Fr. John Jillions, whose thoughtful, open and honest reflections almost always cause me to think. Here is a bit from his reflection on the Feast of Sts. Peter and Paul:
The fact is, bringing the Gentiles in was a massive change, the single most important change that Christianity ever faced. Throughout Paul’s letters we see the trouble this provoked as the universalism of the gospel clashed with the exclusivist position of Jewish Christians (and many Gentile converts) who wanted to keep what they regarded as the full gospel of Jewish tradition. Peter’s own encounter with this question comes in the person of Cornelius (Acts 10-11). Here is this Gentile who miraculously is brought to Christ and experiences the Holy Spirit: what are we to do with him? Thankfully, the early church decisively moved in the direction of embracing Cornelius and the Gentiles and the changes this brought (Acts 15). It wasn’t easy, it took time, even apostles had second thoughts from time to time, but it ensured that the message of Christ was for everyone.
You can read the rest of his short commentary here: http://oca.org/reflections/fr.-john-jillions/june-29-2012.