I think that there are both valid and invalid reasons to resist changes in language. As for most issues, it's not completely cut and dry; but, I don't think that most changes that are made from the bottom up - through the emergent order - should be resisted. It's generally the changes that people try to make from positions of authority that must be resisted.
The English language changes all the time. I rather enjoy the occasional neologism. At the time that Warren Harding took office, the word "Normalcy" wasn't considered a word; but, his "Return to Normalcy" language was effective enough that it ended up in the dictionary.
I was always brought up being told that one should never end a sentence with a preposition. Still, when Winston Churchill was told the same thing, he responded, “This is the type of arrant pedantry up with which I will not put.”
Simple things like, "Everyone needs to turn in his or her homework." evolving into "Everyone needs to turn in their homework." shouldn't be met with too much resistance.
We can also acknowledge that the emergent order doesn't always make perfect sense. It's still odd that, with most pronouns, adding an apostrophe makes it possessive while "it's" means "it is" and "its" is possessive.
Still, we can communicate while not attempting to manipulate by changing the tools that we use to have conversations.
It's when people start using words and refusing to define them or tell us that the words can mean whatever the person speaking the words intends that we need to push back hard. There's no reason to do this but to obfuscate any given point, complicate the obvious, and shield bad ideas from pointed ridicule.
I don't care how noble anyone fancies his or her motives to be when they go on crusades to push us to obscure words like "woman" or "man" or suggest that we say "birthing people" instead of "mothers" because it's "more inclusive".
No, it's the oldest authoritarian trick in the book whether you're aware of it or not.