Downs and Ups

Listen here, you smooth-brained buffoon. You are the kind of person who thinks a "down" is just a direction. You, clearly a walking example of the Dunning-Kruger effect, are incapable of detecting the difference between bad word play and just being a dick. The joke plays on the phrase 'downs and ups', which usually refers to the ups and downs of life, but in this context the pun is on 'Down syndrome'. It's a pretty tasteless play on words, like your personality.