Wisdom is too high for fools; in the assembly at the gate they must not open their mouths.
“Wisdom” and “fools” just don’t mix. After all, wisdom is “seeing life from God’s point of view” and the fool says there is no God (Psa 14:1). Not much common ground there!
Consequently, fools have virtually nothing of value to offer others and giving fools a platform to speak will be beneficial for no one. The proverb says anything they may say among “the assembly at the gate” will not be a good thing. If they do talk, somebody else will probably need to do some damage control!