He’s offended any time someone acknowledges the mountains of evidence that he’s a pedophile. He thinks in terms of good / bad; Loyal / disloyal. If you challenge him in any way, especially on his most shameful misdeeds, he sees you as attacking him viciously. It didn’t matter that she made no statement about it or even asked a really pointed question. Just acknowledging that those files exist and he’s in them is seen as an attack by Trump.