What does Malachi 2:9 mean?

In verse 3, God described His humiliation of the priests in graphic terms. The priesthood would be shamed and disgraced as clearly as if God had smeared animal waste on their faces. They would be discarded as surely as animal filth was removed from the carcass prior to sacrifice. In order to purify the priesthood, and to preserve His covenant with the tribe of Levi, God would judge the priests. Though they were worthy of death (Numbers 18:32), God instead chooses to use shame.

This is both a prophetic statement as well as a description of Israel's current state. Malachi's book of prophecy delivers three main lessons, and the second one is an accusation against the people in general. That charge will involve divorce from their wives and marriage to pagan women. A culture which brazenly joins itself to idol worshippers, and which breaks marriage vows to God, is clearly not one which respects its spiritual leaders. More than likely, the priests of Malachi's day have already seen their reputation in the eyes of the people fading—in no small part because of their own apathy and sin (Malachi 1:13).

As this verse indicates, this is simply a consequence of the priests' own actions. They don't obey God, so there is no reason for them to receive blessing, honor, or wisdom from Him. They don't live lives which reflect the truth, so there is no reason for the people to hold them in high esteem.