If someone stole my car, and I come up to you. Angrily:
"vukmir, some asshole stole my car! I can't believe it! I was late to an important meeting! What a fucking shitbag!"
Would you respond with:
"Woah woah, why are you so angry?"
You know why I'm angry. The only context under which "why are you angry" is even a sensical question is one where the thing I'm angry about isn't worth being angry about. Which is also to say "why are you so angry" necessarily entails the dismissal of the subject the speaker is angry about.
edit:
> "how do you ask someone who is obviously angry why he/she/it is being angry?"
How would you respond to my hypothetical rant above, where someone has stolen my car?