Quick answer
How a person walks is what their fear of God actually looks like. The verse makes conduct the evidence rather than the claim.
Read both lines
The direction of the sentence is worth noticing: it does not say a person who fears the LORD walks uprightly, which is the expected order. It says the one who walks uprightly fears the LORD, reading the posture off the path. That fits the book's own definition at 8:13, where fearing the LORD is hating evil, an orientation of the loves rather than a state of feeling. The second line makes the opposite equally concrete. Contempt for God is not primarily a belief in this verse; it is a way of getting through a week.
Related: Proverbs 8:13 · Proverbs 1:7 · Proverbs 14:26–27
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.