I worked with a guy from Pennsylvania who used the word "whatever" the way some people use the work "like." "I went the the store or whatever and they were out of eggs or whatever and I was really wanting breakfast or whatever..."
I agree with you. It's disrespectful, and dismisses what the person said like it's not worthy of a genuine response. In my opinion, not much different from intentionally yawning, rolling eyes, or similar.
IMHO, whatever is a cop-out or dismissal word that often signals that someone has stopped thinking, assuming they ever started. There's also the possibility of a major disconnect between the brain and whatever.
Whatever could also be used ... When someone tries to provoke you into an argument, and don't want to get into a never ending back and forth, so you write WTVR, meaning you may have the last word. Abbreviation to WTVR would throw the reader off balance. Not willing to admit they don't know what it means. A radio station maybe?
First time I had 'whatever' thrown at me was in the late 70s, a friend said it to me and I found it annoying. She said it a lot, until one day I returned the whatever-fire and said, "What. Ever." Man, did she ever look shocked, but it cured her of the habit. With kids I always found my Nan Stare O Death the most effective way to end any annoying conversation. That, and if there was any attempt to push luck, smiling with "You're not going to like what happens next". I never had to follow through on the latter, heh heh, and to this day my grandson (now a teen) does not realize that I had absolutely no follow up re what would happen next. At any rate, I digress. 'Whatever' irks the hell out of me if said to me, otherwise I'm totes 'whatever' to the use by others, lol.