Many things combine to make the present inroad of false doctrine peculiarly dangerous.
1. There is an undeniable zeal in some of the teachers of error: their “earnestness” makes many think they must be right.
2. There is a great appearance of learning and theological knowledge: many fancy that such clever and intellectual men must surely be safe guides.
3. There is a general tendency to free thought and free inquiry in these latter days: many like to prove their independence of judgment, by believing novelties.
4. There is a wide-spread desire to appear charitable and liberal-minded: many seem half ashamed of saying that anybody can be in the wrong.
5. There is a quantity of half-truth taught by the modern false teachers: they are incessantly using Scriptural terms and phrases in an unscriptural sense.
6. There is a morbid craving in the public mind for a more sensuous, ceremonial, sensational, showy worship: men are impatient of inward, invisible heart-work.
7. There is a silly readiness in every direction to believe everybody who talks cleverly, lovingly and earnestly, and a determination to forget that Satan often masquerades himself “as an angel of light” (2 Corinthians 11:14).
8. There is a wide-spread “gullibility” among professing Christians: every heretic who tells his story plausibly is sure to be believed, and everybody who doubts him is called a persecutor and a narrow-minded man.
All these things are peculiar symptoms of our times. I defy any observing person to deny them. They tend to make the assaults of false doctrine in our day peculiarly dangerous. They make it more than ever needful to cry aloud, “Do not be carried away!”
~ J.C. Ryle
Taken from : Warnings to the Churches, “Divers and Strange Doctrines”, [Carlisle, PA: Banner of Truth, 1967], 76, 77.
Note: Apart from what is given above by J.C. Ryle, I can say that in context of the times we live in, the love of money can also cause preachers to willingly stop preaching true doctrines and instead preach false doctrines, so they are overloaded with dollars, pesos and yens in return!