Why do people believe and preach false doctrine?

For example: It has been asked (on Yahoo! Answers) "What is up with Matthew 16:27-28?" by ITS A TRAP. A lot of false teachers will tell you that this is referring to when Jesus rose from the dead three days after he was crucified - as if they pay no attention to verse 27 and make up their own doctrine around verse 28 or they just never read the bible and just believe whatever they've been taught by other false teachers like themselves. Did Jesus reward every man according to his works when he rose from the dead after his crucifixion? NO! I'm sure John fully understood these two verses when he was in the isle that is called Patmos. These false teachings and false doctrines are why some people are so quick to turn their noses up to the bible. The bible does not say "the earth is flat." The bible does not say "money is the root of all evil." The bible does not say " spare the rod, spoil the child." And a rod does not mean a switch, it means a walking stick. THE BIBLE DOES SAY "The legs of the lame are not equal: so is a parable in the mouth of fools." Why do people believe and preach all this BS?