from John Piper, "Watch Out For Those Who Would Lead You Away From the Truth" (2006):
"Romans 16:18: 'For such persons [that is, the persons who depart from the doctrine] do not serve our Lord Christ, but their own appetites, and by smooth talk and flattery they deceive the hearts of the naive.'
"Let's take the second one first. Verse 18b: 'By smooth talk and flattery they deceive the hearts of the naive.' The word for flattery is simply blessing. And smooth talk doesn't necessarily mean manifestly slippery. It just means pleasant and plausible. So the reason we must be so vigilant over biblical doctrine is that those who depart from it take simple people with them by pleasant, plausible speech that presents itself as a blessing. False teachers don't get a following by being rough and harsh. They get a following by being nice.
"Just take two examples from history: Arius (d. 336) and Socinus (d. 1604)—both of whom denied the deity of Christ. Parker Williamson describes Arius like this:
Here was a bright, energetic, attractive fellow, the kind of citizen whom any Rotary Club would welcome. Singing sea chanties in dockside pubs and teaching Bible stories to the Wednesday night faithful, this was an immensely popular man. His story reminds us that heresy does not bludgeon us into belief. We are seduced.
"And another writer describes Socinus like this:
He was a gentleman. His morals were above reproach and he distinguished himself by his unfailing courtesy. Unfailing courtesy was remarkable in an age when even the great Protestant leaders, Luther and Calvin would use vile street language when arguing with their opponents.
"This means that it will seldom be popular to resist false teachers in the church because they are almost always perceived as bringing a blessing and speaking with winsome words. They are gentlemen. And Paul says the innocent are carried away. Hence he says, 'Watch out for them. And avoid them'."