WHAT ONE'S REACTION TO REBUKE REVEALS
Pr 9:7-9 Whoever corrects a mocker invites insult; whoever rebukes a wicked man incurs abuse. Do not rebuke a mocker or he will hate you; rebuke a wise man and he will love you. Instruct a wise man and he will be wiser still; teach a righteous man and he will add to his learning.
Likewise it is written, "Whoever loves discipline loves knowledge, but he who hates correction is stupid." Pr 12:1 And conversely, "One who rebukes a man will afterward find more favor than one who flatters with the tongue." Pr 28:23
So if you want to find our how stupid a person is, trying correcting them.
Pr 15:12 A mocker resents correction; he will not consult the wise.