I love jokes, and telling jokes, so I would be in big trouble. But there is plenty of bad laughter around. On a school playground you can see mean kids laughing and mocking an unfortunate child. Mary is retarded. Mary is retarded.
Some people laugh and sneer at everything good and beautiful.
There used to be a practice of hazing new recruits in a regiment, or freshmen in college, and that was done by humiliating and making fools of them. When you are laughing at poor people, and mocking immigrants, and despising simple-minded people, you are not crying out to God for the wisdom of the Spirit to care for them and love them. So you can see that the sermon on the plain is using three strong metaphors to show us the blessing of feeling our need for God. Instead of relying on money to solve our problems, we feel spiritually poor and look to God to meet our heart needs. And instead of mocking and sneering and laughing at others, we cry out for the wisdom that comes down from on high.