The gospel, by definition, is a matter of telling. It is communicated by word. Yes, our actions do sometimes speak louder than words. But we cannot convey the message without telling the message. And the message of the cross of Christ will always be at cross-purposes with the message of the cults.
Confrontation is a necessary part of evangelism.
We will have to pay the price of educating ourselves to the beliefs of the cult system we encounter. Three things you can do First, determine to preserve the relationship. Commit to approach the subject carefully and prayerfully. Remember that all ministry comes through a spirit of brokenness. Arrogance and anger have no place in ministry.