Gamers sometimes have a solipsistic approach to their preferences, and end up investing so much into a specific game that they struggle to get anybody else to play with, that it tends to boil over in frustration and bitterness. I’ve communicated with people that refuse to play D&D of any particular edition, d20 games, White Wolf games, indie games, traditional rpgs, any particular edition of Traveller, “any game that uses percentile dice” and so on. The views expressed are quite adamant, and are usually accompanied by an incessant push for Their Favourite Game, be that what it is.
Edition warring isn’t exclusive to D&D. I remember play testing the Mongoose Traveller game back in 2008, and there were people banned for endlessly insulting others based on edition preference, or trying to attack the possibility of a new game. I remember when Mage Revised came out, which was incredibly bitter too - where fans would end up posting negative reviews of supplements online before they came out, etc.
A lot of edition wars do require the game publishers to address underlying concerns, but the reactions from fans can be heavily hyperbolic, entrenched and personalised quite quickly. What that says about human nature, I dunno. IMDB is worse.
