The word imbecilic comes to mind.
I hadn't realized how fitting the word actually is. Here is what I found.
im⋅be⋅cile /ˈɪmbəsɪl, -səl or, especially Brit., -ˌsil/ Show Spelled Pronunciation [im-buh-sil, -suhl or, especially Brit., -seel]
See images of imbecile
–noun
1. Psychology. a person of the second order in a former classification of mental retardation, above the level of idiocy, having a mental age of seven or eight years and an intelligence quotient of 25 to 50. Wow!
2. a dunce; blockhead; dolt.
–adjective
3. mentally feeble.
4. showing mental feebleness or incapacity.
5. stupid; silly; absurd.
6. Archaic. weak or feeble.
Origin:
1540–50; earlier imbecill < L imbēcillus weak; -ile r. -ill by confusion with suffix -ile
Does that fit this guy to a tee, or not...