No, it's not a consideration for me since the term altcoin for me in reality is more respectable than XT by far.
I'd say the definition of altcoin covers it because it covers all rule changes that incurred bifurcations in the past as well, this undoubtedly should carry weight when considering the definition of this word. But if I were to choose, I'd pick another word like "altfork" or something like that. Altcoin flatters XT in my opinion.
The only thing I like about it is that apparently it offends and irks some tiny, tiny men.
I accept the definition as it's widely accepted and this is the most important consideration for definitions.
As for the rest of your argument it actually just comes down to an appeal to authority and an appeal to the majority.
https://en.wikipedia.org/wiki/Argument_from_authority
https://en.wikipedia.org/wiki/Argumentum_ad_populum
Words work exactly like that, they are defined by authority and popularity, not because some enlightened or self-important person settled the matter. At least not in the general case.