I think that trying to present it as that there’s somehow one set fixed golden irrefutable version of the “lore” and everything else is breaking it is somewhat of an overstatement.
It’s one thing if you’re dealing with someone who’s like, “My character’s name is James Bond and he was sent to this universe by a Time Ray used by the great villain Magneto but when I got here I found out that I’m actually the king of this Storm-Wind place so you need to treat me as such.”
It’s entirely another if you’re dealing with someone who’s like, “Hello, I’m a Death Knight and this is my wife” and then have a WoW Wiki battle where you have to dredge out receipts from a dozen different stories, quests, throwaway NPC lines and Q&As that say or don’t say that Death Knights can still have emotions and attachments. That fight is something that damages the “health” of the RP scene much more than people being flexible in gray areas.
The lore is a mess. It conflicts. It was hodgepodged together like a vast ramshackle Howl’s Moving Castle of contributions from quest writers, developers, third-party writers for books and stories and various other random people over time, many of whom are no longer at the company and can’t explain their intent or clarify anymore. It has also been my personal experience that anyone who tries to present themselves as a lore “expert” who knows the “real” lore in every given situation is almost always relying on half-remembered bits that they picked up on through word of mouth and imagining what makes sense in their head (a.k.a. “headcanon”) , or they’ve fixated on something from old lore that was subsequently retconned or clarified.
At the end of the day, though, the lore doesn’t need defending. There’s no point. Blizzard doesn’t care that much, they don’t even care if someone wants to James Bond, the King of Stormwind it up. Why should we? All rabbling amongst ourselves does, turning it into a one-upsmanship game of My Character Is More Lore Accurate Than Yours, is divide the community and turn people away from the hobby as they feel judged and disregarded.
There’s nothing wrong with personally preferring to stick with what your understanding of the lore is as closely as possible for your characters and stories. That’s totally fine! I actually largely prefer to do the same. I find that working within the framework of the story and events as given, according to my understanding of them, is a fun challenge even when the developers like to randomly throw in a new twist like a three-year timeskip that I will die mad about. But, a person’s personal preferences should end at the tip of their own nose.
If someone is playing something that you don’t want to go with, just move on and do something else. There’s no need to argue with them about the “accuracy” of what they’re doing, and more importantly, they haven’t done anything wrong just because they choose to be more flexible with the lore and setting or even reject it entirely. They’ll get people to play with them, or they won’t. There’s no crime in having different preferences.
Just move along and find people whose preferences and interpretation of the lore aligns with yours. That’s one of the glorious things about MG Alliance being so populated, is that no matter what you want to do you can almost always find a group of people who want to do the same.
There is no lore INSISTING that is the case.