Kirk and crew disliked what the Klingons did in TOS not how they ate or smelled
...But before ST5:TFF, they hadn't seen
how Klingons eat!
Really, I'd say it's a sort of natural progression for our heroes to first hate the people who fly the starships that rain destruction on innocents; then to hate the soldiers who plot and scheme and then smile; and then to hate the very stench of the scum. They learn more and more about the enemy in the two decades of adventures, and there's no particular reason for them to suddenly change course and start treating the new evidence as being somehow favorable for the Klingons. It's easy to be "rational" about hatred and argue that if the Klingons just stop being so damn evil, hatred can stop as well - but unlikely that our very human heroes would actually be able to behave
that rationally even if a single Klingon or three prove they are slightly less rotten than the lot.
Goons like the two assassins might say they hate the smell of Klingons without ever having smelled one. Our main heroes might quite plausibly start hating the smell of Klingons, and saying so, after
having their first opportunity to witness the odor.
Chekov of course was always
racist about the Klingons - but perhaps he had actually smelled one, or several, prior to "Trouble with Tribbles"? There's that brother Pyotr backstory, and only Sulu's (uninformed?) word that it ain't real...