Such teachings come through hypocritical liars, whose consciences have been seared as with a hot iron. 1 Timothy 4:2 (NIV)
We all have an inward knowing of right and wrong plus the accompanying urge to do the first and keep clear of the second. This is conscience.
When we keep practice of ignoring, resisting and rejecting our conscience where we do what we clearly know is wrong and not do what we clearly know is right then our conscience gets seared or burned as with a hot iron so to speak and consequently we are no longer sensitive to what’s right and wrong. We lose that feeling of either unease for doing wrong or assuredness for doing right. It’s like a person who commits a gruesome murder and not feel the least bit bothered.
So false doctrine is taught and perpetuated by people whose hearts have been seared as with a hot iron because they continued to reject the truth of the Gospel of Jesus Christ and instead believed the deception of the traditions of men.
It’s very hard to help such people turn and change because they’ve thrown themselves beyond conviction. We only have to avoid them and not argue with them.