I wish I could say that was an un-heard-of event.
The first year 4e was out, I had the bizarre experience of watching a player sit down at a 4e table, declare he was trying it for the very first time, choose a rogue, complain bitterly about being 'forced' to use a dagger, and just generally dragged the whole thing down. Twice. In two separate games, on two different days.
Guess I don't look too distinctive at a convention, or he might've recognized me and moderated his behavior, or at least changed up his initial spiel.
And, yeah, famously, books were burned.
The edition war went beyond a torrent of on-line nerd-rage. It was a toxic culture. Like any other form of bigotry, but all the more uncompromising because the subject was so trivial.
Some of it also became visible only in retrospect. A convention I used to go to was very cold to the idea when, in 2008, I submitted a proposal to run a short introductory game of the new edition - 4 players, 4 hours - as a gimmick. Too short. They'd never allow 4-hr games. I shelved the idea, but improv'd it in open gaming because there was interest, anyway (5 min prep, including re-skinning a monster because there were no water elementals the right level).
2014, I get an email from the same con - run a half-session (4 hr) game to introduce 5e and get the same credit as running a full session. Mind you, I was enthused about 5e and ran a bunch of them - converting In Search of the Unknown, Village of Homlet, Sunless Citadel, the first chapter of Council of Thieves, KotSf (shudder), and Twisting Halls, each to boiled-down, 4-hr 5e adventures. It was a blast. I was in an altered state of consciousness by Monday morning.
2008, little disappointed, still ran a great game; 2014, excited, exhausted, had a great time … but, y'know, in retrospect, that was quite the change in attitude.
I'm not sure which is worse, the digs at 4e in passing, or pretending it never happened?
I'm not sure I follow. Hussar & I have both pointed out that a lot of little things "DNA" made it from 4e to 5e. They're not things that made 4e 'great' (good at what it was good at - balanced, playable, genre emulation - I'm sure you can throw out a few Forge labels I'd rather not use), at least, not in the form they made it into 5e, but among them are many supposedly-intolerable concepts that, in the context of 5e (with The Primacy of Magic restored!), are now fine.
Oh, wait, I think I see what you mean: Yes, yes I am. I did the same thing to grognards grousing about 3.0, too. You get a complaint that the new edition sux because it lacks X, you point out that X is, in fact, right there, they get mad at you. I'm glad you have the patience to explain the synergies and emergent characteristics based on the subtle differences in how (or greater degrees to which) X (& Q & Y & Z) are /implemented/ in the old edition, don't arise in the new (again, if I'm getting the allusion).
I've just had to do it a /lot/ more since 2008, rarely with anyone showing the same kind of patience & expansion upon their issues as you're up for.