You know what? Yes. Yes he did. He did because he had the misfortune to be pulled into Homer Simpson's world and he couldn't bring himself to just accept Homer's good-natured dimwittedness just like Lenny, Carl, Mr. Burns, Smithers, Marge, Bart, Lisa, and every other character on the show has learned to do. Grimes' efforts to convince everybody at the plant that Homer was not the good person they saw him as led to his self-destruction when they chose not to listen. For, you see, it was another example of the real world colliding with the Simpsons' world, and when the two walk into a room, only one ever comes back out. Anybody who exerts all their energy into forcing their beliefs on a society that would rather not conform to those beliefs is wasting their precious time. It's not happy, but it's the truth.
It's an extremely complex episode that not very many people like to analyze. If they did, though, perhaps they would see it in a new light.