that's kind of
stupid
unintelligent
ignorant
dense
brainless
mindless
foolish
dull-witted
dull
slow-witted
witless
slow
dunce-like
simpleminded
empty-headed
vacuous
vapid
halfwitted
idiotic
moronic
imbecilic
imbecile
obtuse
doltish
gullible
naive
thick
dim
dumb
dopey
dozy
crazy
cretinous
birdbrained
peabrained
pig-ignorant
bovine
slow on the uptake
soft in the head
brain-dead
boneheaded
lamebrained
thickheaded
chuckleheaded
dunderheaded
wooden
wooden-headed
fat-headed
muttonheaded
daft
barmy
not the full shilling
thick as two short planks
silly
scatterbrained
crackbrained
nonsensical
senseless
irresponsible
unthinking
ill-advised
ill-considered
inept
damfool
unwise
injudicious
indiscreet
short-sighted
inane
absurd
ludicrous
ridiculous
laughable
risible
fatuous
asinine
pointless
meaningless
futile
fruitless
mad
insane
lunatic
cracked
half-baked
cock-eyed
harebrained
nutty
derpy
cuckoo
loony
loopy
zany
screwy
off one's head
off one's trolley
out to lunch
potty
dotty
batty
gormless
glaikit