Watanuki was just telling him why he smelled good!
Would you rather him think that there's no REASON why he think someone who smells like food?! Let him think he just thinks there's some random people he wants to eat?!
Watanuki just told him the truth. If he can't deal with it, that's HIS problem and it's not Watanuki's fault so BACK OFF! [A-and have a super strong girl shoving you HARD.]