Heresy is what I see to be at variance with what I believe to be true. Cultic is the control of a group by an idea or its leader. The two realities are common to the Christian church.
Before we too quickly assume we can detect what really is heresy and what is cult-like, consider this question: What did the early church first understand to be the importance of Peter's visit to Cornelius' home?
Peter, at first useless to the agenda of the Spirit, had no heart to respond to the spiritual inquiry of this Roman, Cornelius. Peter first needed transformation (see Acts 10). Imagine him explaining to the disciples in Jerusalem why he went to minister to a Roman and his household. This pagan. This hated military presence.
Today we face shifts in culture and new expressions in the church. Some of the postmodern "stuff" I like, others I don't. What I'm careful of is to quickly dismiss their concerns.
For you see, I was raised in a Pentecostal world, a world many looked on as heretical and somewhat cultic. I have too sensitive a memory of having been dismissed out of hand to do too quickly the same to others.
Leaders are called on to take a longer view: to see within restive minds an authentic search for the Lord. It is too easy to fall into a trap of marginalizing one who might fall slightly outside my borders.
Prayer—
God of truth, forever brooding over the "birds" of your making, keep me from rejecting what I see to be the "ugly duckling" because he or she is different from me. Help me know they too are yours. In your love and grace I offer this prayer. Amen.