disillusionizer
dismayer
obviator
nonthinker
shunner
disannuller
nonsympathizer
ignorant
mishear
confounder
unsympathizer
underestimator
disfavourer
smart aleck
disheartener
overstater
disprover
mishandler
scepticist
neglectee
layman
denigrator
displeaser
confusionist
ignorer
misseller
Monday-morning quarterback
unthinker
nonaficionado
doubter
overestimator
miscegenationist
quasher
negativer
unrespectable
insensate
sad ass
distortionist
nongenius
miscegenist
joker
resenter
dissuader
would lose one's head if it wasn't attached
deranger
contradick
expugner
unalive
dishonourer
overthinker