Half Left or Half Right

Listen up, you smooth-brained simpleton. This 'joke' isn't complex, unlike your family tree which is probably a circle. The first guy asks if someone is politically 'half left' or 'half right'. This is usually about politics, get it? Politics! The second guy says 'neither, in-between.' This sets up the punchline. The first guy then delivers the 'zinger' which is a vulgar insult implying the second guy is a grown man who still sleeps between his mom's breasts. It's gross, it's an insult, and it suggests the guy is an absolute loser. Get it now? Or do I need to draw you a picture with crayons?