So... all she says is, そういうの嫌い "I hate this kind of thing". Dino-Takafumi is depressed because it's tantamount to saying, "I hate you" in JP. Fujimiya is pleased with how much this upsets him because it essentially confirms that he does like her back.
I get that cultural differences mean some liberties have to be taken with dialogue, but I feel like "Quit acting like a shithead" doesn't really fit. Something like, "I hate you when you're like this." would explain better, for example, why he refuses to use magic next chapter and why Fujimiya is delighted by this.