2 . DO NOT push your church or denomination. DO present Christ. It does not. DO NOT argue. Losing your temper will spoil your credibility and your chances of talking to him again.
Cultists are masters of changing the subject and avoiding the issue.
If he is wrong about the gospel or the Person of Christ, he is wrong enough to lose his soul. Next to the Cross, every other topic pales in significance. One of the worst examples of this came when we were witnessing at a Way International convention in coordination with a number of other Christian churches. There was a team there completely lacking in emotional maturity. We arrived at the Way convention desiring to present to Way members our corporate, spiritual unity with every other Christian believer there, but within three days we were telling confused and irate Way members that we had nothing to do with the shouting stompers.