Haters gonna hate, the same people get irrationally angry at all kinds of other things too. Women, the gays, Europe, you name it, they're gonna hate it. There's always something and someone they have been angry about, through some perceived yet nonsensical mechanism.
But it is irrational, you're unlikely to argue them out of any of their opinions, not unless you're planning to embark them on a thorough course of cognitive behavioural therapy. I don't know why people engage with them, they want the argument, you won't win, you can't impose rationality on irrationality. If your day is ruined to the extent you spend the entire afternoon ranting about being held up 10 seconds to overtake two cyclists in the morning, I think you need to take a good, hard, critical look at your life. They won't, of course, the main benefit of being dim and angry is that you lack the cognitive abilities to realise you're dim and angry.
Of course, this irrational anger does put a significant number of people off cycling, at best it's harassment and shouldn't be normalized, and shouldn't be a cheap and routine diatribe in newspapers and online and a staple of radio talk shows.