Yes, goons can be a stupid, dull underworld type person, (and i think of the kids movie The Goonies, but goons can be low life thugs..
I. E., "He couldn't pay the loan shark the vig, and a couple of goons worked him over, to send him a message"
Goons, in this case would be similar to thugs or strong arm men... they might not be the brightest bulbs, they are better known for their muscles, rather than for being stupid.

(*vig= vigorish- perhaps from the russian or ukrainian, vygrash or vyigrysh, which means winnings or profits.. used in US since 1912 to mean interest charged by loan shark)