when you don't actually care bout getting bullied and u say this

trying to annoy someone that has no idea whats going on.

When he's making soup in the microwave and you just have to ask, why?

Because who makes soup in the fricken microwave? It might make you angery, so you just come in with your shirt over your head and ask, "y u makin soup?"

An internet meme. Usually shown in dolanduck comics which are great comedy. It's also said by idiots who present them selves with as trolls and disgrace themselves. I can understand dolan duck comics stating "y u do dis". But when a person says it it's incredibly idiotic. They honestly make themselves look like fools in front of everyone.

"y u b h8tn?" is an internets-term that was made up by the member Jonas over at NarutoForums (me who's writing this).
As you may figure out, the word is internets-language for the word "why you be hating?".

Derives from the phrase "Why are you so easy?", which is how one with many hours inquires why the person they just killed was of low skill.

knowing that he/she is upset, they tell u there not upset, but you make a joke out of it and ask them why their angry knowing the answer already and just to make him/her more upset.