We shouldn’t be surprised that dangerous false teachers can be very friendly. So can cannibals.
The only difference is that while cannibals devour flesh, false teachers devour souls.
Gary Hogg’s “Cannibalism and Human Sacrifice” gives an example of a particularly winsome group of cannibals: “He [Herbert Ward, who traveled the Congo] found, in addition to the cruelty and degradation, abundant good-humour—a quality that subsequent travellers and settlers have frequently mentioned.” Ward writes,
The impression I received from personal intercourse … was that the cannibals of the forest were infinitely more sympathetic than the people of the open country, where the trading instinct is inborn. The cannibals are not schemers, and they are not mean. In direct opposition to all natural conjectures, they are among the best types of men.
Thus the cannibals appeared outwardly as “the best types of men,” yet in murdering and eating humans proved to be inwardly wicked. These traits of appearing righteous while being rotten within likewise applies to false teachers. Scripture says:
“For such men are false apostles, deceitful workmen, disguising themselves as apostles of Christ. And no wonder, for even Satan disguises himself as an angel of light. So it is no surprise if his servants, also, disguise themselves as servants of righteousness. Their end will correspond to their deeds.”
(2 Corinthians 11:13-15)
“Beware of false prophets, who come to you in sheep’s clothing but inwardly are ravenous wolves.” (Matthew 7:15)
So don’t judge a professing teacher of God’s word by the size of his smile or the gentleness of his words. Judge him by the Bible.
If you don’t, your soul might be cannibalized.
Wolves Among You
 Garry Hogg, Cannibalism and Human Sacrifice (New York, NY: The Citadel Press, 1966), 107.