Ah, I do like it when you get a little filthy-mouthed.

[ He winks at her. What a joy he is. ]

But with regards to that...Who's to say? Ezar is - hm - capricious. My best guess for his primary motivation would be silencing a critic of Piotr Vorkosigan's power. Or perhaps he does like us outsiders - he might very well be curious about us. Or, honestly, he might simply be testing out Negri's abilities. He does things because they're interesting to him and he wants to see what happens.