[Mainspark]

I think to some degree that intense dislike of Cubs fans dates back to the mid-1980s, when the team began to enjoy some moderate (although nothing approaching ultimate) success.
Being a Cubs fan became an in-thing among Yuppies of that period, at least here in the Midwest.
It was extremely irritating (to Reds and Cardinals fans, and probably even to longtime Cubs fans) to hear these novices suddenly "talking baseball" as though they were veteran observers of the game, even though their knowledge was limited to what they had learned from listening to Steve Stone.
As a result, Ryno was the greatest player of all time; Sutcliffe was the greatest pitcher of all time, etc.