You are trying to! It's not like you want to listen to his shouting, you want to lick your dragon sized Popsicle in peace! You half listen to what he says and then grow very bored. You notice that he is wearing a lot more grey than he normally does, maybe that's why he's so grumpy? If he were you, which he's not, you would be grumpy to! Covering such wonderful smelling candy red with bleh grey would make anyone shouty and mad! Maybe he just needs some more color in his life!

Speak of the devil!
Terezi: Examine colorful creature who's just appeared