Related Clues:

• Birdbrains
• Dunces
• Dumbbells
• Chowderheads
• Boneheads
• Dim bulbs
• Putdown of those with whom one disagrees
• Dimwits
• No-brainers?
• Tomfools
• Schmoes
• Imbeciles
• They're thick
• Morons
• Other drivers (never you, of course)