Definitely confirmed in Megamorphs 3. He has an internal debate in the beginning, and mentions he feels like he has to turn in Cassie for her potentially treasonous thinking because if you're black or Jewish, you have to be extra careful to stay on the government's good side as a loyal party member.
[spoiler]"Yeah, it would be a pity if some of the Primitives escaped alive," Cassie said.
I shot a look at her. Had that been sarcasm?
She smiled blandly.
I had long suspected that Cassie might have slightly radical tendencies. A lot of blacks did. Blacks and a lot of Jews, although not in my family. My dad was a certified POE - Patriot of Empire.
Still, if you had any Jewish blood in you at all, you had to be extra careful so no one thought you were a radical.
I knew Cassie was soft-hearted toward her own slaves. But I'd never heard her make any kind of subversive remarks about the war. I'd always just assumed she was sentimental.[/spoiler]
There was at least one other instance it was mentioned, I can't remember when though.