All of Strange's justifications are melting away thanks to Childermass's cold logic. Because he's right. These are the fae they're talking about, beings of wonderful power who could easily drop him at a moment's notice. He's certainly useful: he knows he is. And he'll prove it to the Summer Court no matter what.

"I--" And then Strange cuts himself off, glaring at Childermass. He's the one in charge. If he doesn't want to have this conversation, then he won't have this conversation. "I certainly don't need to justify myself to you. And if you had any sense, you wouldn't be challenging me to begin with. Remember: you're under my thrall. And I haven't decided how best to punish you for that cat nonsense."