Part of the quarrels run, and the second of three verses on the same figure.
Quick answer
The kindness is the warning sign, not the reassurance. The verse tells you what to do with it: do not believe him.
Read both lines
The NKJV footnotes the first line as literally his voice is gracious, and the instruction attached to it is unusually direct for this book. Proverbs normally describes; here it issues a command about a specific person in a specific moment.
Seven abominations is the number of completeness again, and it deliberately echoes 6:16–19, where the LORD hates six things, yes seven, and the list runs from a proud look to sowing discord among brethren. The echo puts this man's interior in that company. The caution the verse asks for is narrow and worth stating: it is aimed at someone already identified as hating, in verse 24, and it is not a license for general suspicion of kind people.
Related: Proverbs 6:16–19 · Proverbs 26:24 · Proverbs 27:6 · Proverbs 20:6
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.