Quick answer
People listen to what suits them. The verse observes that an audience is a kind of confession.
Read both lines
Both halves describe listening rather than speaking, which is the unusual move. The book normally warns about the liar's mouth; here it watches his ears. The NKJV footnotes "spiteful" as literally destructive, and the picture is of someone leaning in toward exactly the speech that will do damage. What the verse implies is uncomfortable and useful: a slanderer needs a listener, so the person who eagerly receives the report is not a bystander to it. What you are willing to hear says as much as what you are willing to say.
Related: Proverbs 26:20 · Proverbs 20:19 · Proverbs 17:9
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.