Xel will stop being scoffy in favor of sympathy now, because although he doesn't know Da Vinci he does know enough about draftsmanship, if not this-world art, to be impressed by quality and a loving pen. But he does say who on earth are these Sforza, they sound incredibly pedantic-minded in that bullish ale-quaffing kinda way.
Xel raises his hands and says he does not know from Spain! Testostabourniel (it got shortened over time) just happens to eventually occupy the same geographic location! And what he has against them is they perfume their hair instead of bathing, and have very little gender parity, and treat any citizen who can't wield a sword effectively as a slave (thus the gender issues; swordswomen got respect there until a few centuries ago), and their cuisine is so hot-pepper oriented that they think oil is a sauce if you slice a chili into it. Also the whole stealth-intelligence thing, which is fun in theory but gets kind of annoying with constant exposure.