Gallifreyan removed "x-men" tag from this question. Why is it wrong for this question to have "x-men" tag?
Probably based on the tag wiki
My best guess is that the editor was following the guidance in the tag wiki:
Use this tag to refer to the mutant superhero team in the Marvel Universe.
As such, questions about characters appearing in X-Men comics but not belonging to the the X-Men team would seem to be excluded. The question edited was such a question, asking only about Apocalypse (a mutant who does not belong to the X-Men).
However, it may be that x-men is/should be used for any questions about X-Men franchises. I’m not sure whether this question has ever been brought up, so perhaps current usage, whatever that may be, should be the guide.
Most other teams like this, or even individuals, were explicitly made franchise tags during the recent cleanup. This was simply missed then, otherwise I would have added it to more questions and updated the wiki.
Since that's all said and done, changing it now probably needs a consensus.
But to match current usage it should be updated as in: