One could also see it as an Aesop against petty grudges or standoffish behaviour, with Homer's fanatically spiteful retaliation towards one slight doing far more damage to him, his family and the whole town, when just amicably filing a complaint could have likely quickly solved things.
Idiot Ball: Marge. Did she really not know her husband that well, that if she told Homer the truth about forging his name on an apology letter, it would set him off on a crazy rampage which would result in destruction of the town? She could have just stayed silent and let Homer believe he did beat the city hall. Granted the implication was that Homer's gloating was so insufferable that she couldn't hold it in anymore.
Strawman Has a Point: While he retaliates to a detrimentally spiteful level, Homer was entitled to be unimpressed by the workmanship of the garbageman. They brushed him off when he was in clear sight with his garbage, only coming back to threaten him after he snapped at them in response (and complain about his lack of civility after Love Day) and later beat him up, while also refusing to collect his trash. Homer could have easily complained about the negligence to Patterson or outright charged for public assault, rather than following Marge's direction of apologising to them or his own direction of stealing Patterson's career. In Marge's defense, Homer wasn't exactly clear about what started the fight, and from the way he described it he made it sound like he pissed them off for no reason.
Values Dissonance: The idea of electing a sanitation commissioner can be somewhat bemusing if you live in a community where trash pickup is either overseen by an appointed public official, or if trash pickup is simply contracted out to a private business.
Values Resonance: Similar to Being There, this episode satirizes the trend of style overwhelming substance in media and politics, as Homer is elected by making outlandish promises that are ultimately impossible to keep, which Patterson attempts to warn Springfielders of. Comparisons have been made to Donald Trump's campaign against Hillary Clinton, where someone with no experience wins against an experienced official by making crazy promises and insulting their opponent.