For 2Timothy 4:2, "Preach the word; be instant in season, out of season; reprove, rebuke, exhort with all longsuffering and doctrine."
a deeper meditation is necessary.
Since it has to do with both rebuke and longsuffering, I shall generalize it simply this:
When it concerns personal influence, association of reputation in fellowship, and false doctrnes are preached, then there must be head on collision.
When it is but discussion, preaching, teaching, preparing to agree to disagree, non-association of ministry, there is no need to attack the vipers but merely question to reveal their own folly.
On the side note, recent talk with my mother on a particular group of the "non-judgmental" type called BSF (Bible Study Fellowship) urged me to take on this group. Since it so much emphasizes on not being a denomination, I'll not be too anxious to call it anything but a particular fellowship group. After all, to be qualified to be called a denomination, a group needs to be willing to have fellowship with other denominations in both similarities and especially dissimilarities, not a rejection of all other denominations and claiming themselves the only ones biblical.
But I need not take on another non-denomination group. Its shallowness and problems have been well documented everywhere. And I have already covered similar errors.