[Consider this scenario:

Person A privately tells you that Person B acts “holier than thou”.

What should you think?

Obviously, if you did not witness the event that A claims to have occurred, then the answer must be a guess.

What if Person B said something judgmental, but in the humble way of suggestion?

What does A’s comment imply?

Well, Person A may be projecting ‘his’ own attitude of moral superiority onto Person B, interpreting B’s humility as haughtiness.   Person A feels anger and imagines it to be an expression of B.

To A, B has acted how A would act, if given the opportunity.

In this case, A projects ‘his’ own character onto B.]