I guess we'll just have to agree to disagree on this issue. Let me reiterate though that I think it's rude only in a heads-up situation. I really don't have a problem with it in a multi-way pot.
My point was that online it's unnecessary when you are heads-up because you can see your opponent's total amount of chips right in front of you. You know immediately that you have them covered. It's a much different scenario than in a live game, where it can be much harder to tell if you have someone covered and therefore you ask for a count. And I have never, ever, seen a player in a legitimate live game ask for a count, get it, and then bet his opponent's exact stack size. It's always "I put you all in" or just "I'm all in." Maybe I'm just too old-school.
I will say that I agree with you that it's up to me to not let it affect my mindset or play. Fortunately for me, it dosen't.