I agree with all that (though I've never dabbled in the dizzy literary heights of Harry Potter). I'd go further to say that I object to people who express these sentiments who then go on to say that we should "practise tolerance" or similar. To tolerate is uncomfortably close to "to put up with." Difference, diversity, variety, individuality, all attributes of humanity that we should want to celebrate, not tolerate. My old mum used to say that people with tattoos should be thrown in jail...

When it comes to "one" as a pronoun, it can seem a bit stiff and formal:

"One's dentist should tell one of the best way to use one's toothpaste with one's electric toothbrush."

Or:

"Your dentist should tell you of the best way to use your toothpaste with your electric toothbrush."

One sounds distinctly awkward and the other sounds a bit too direct (I've been accused of using "you" in that manner too personally when I hadn't I intended it, especially by Americans). The answer, as ever, is to rethink the sentence from scratch rather than hanging on for dear life to your beloved literary mini-creation...