What do you mean "that's not a thing?" I don't believe he's ever explicitly called himself a Marxist but he has cited Marx as an influence on his works, as a professor of economics.
One of Harris's most notable contributions to economics is his 1978 monograph Capital Accumulation and Income Distribution, which is a critique of orthodox economic theories that provides an alternative, synthesizing the work of David Ricardo, Kalecki, Marx, Roy Harrod, and others. Harris employs mathematical modeling to explore the relationship between the accumulation of capital and income inequality, economic growth, economic instability, and other phenomena, arguing that typical theories fail to adequately consider power, class, and historical context.
It seems basically true that he's a Marxist professor of economics. It's just not really relevant to Kamala since she's an entirely different person.
I'm happy to criticize China on its actual faults, but I'm not going to jump to conclusions based on inadequate or inaccurate information. The standard for evidence is much lower when it comes to criticizing China, most of the media we consume comes from Western sources, and people just don't have firsthand experience and will believe just about anything, and so I may push back more simply because there is more bullshit to push back on.
You accuse me of "mindlessly endorsing" everything they do, but there is stuff I criticize and when I don't, I explain my reasons quite thoughtfully. What I don't do is mindlessly criticize everything they do (or are accused of doing, or assumed to be doing, without evidence) which is pretty much the standard that people expect from me. There's countless accounts on here that only ever criticize China and do so without providing explanations or justifications for it. They don't even come up with any original quips, it's all just lazily repeating "haha Winnie the Pooh" to each other with zero thought or analysis. Generally, these people could only name one or two events from Chinese history, and have no interest whatsoever in learning about or understanding their perspective, which makes having an intelligent discussion on the subject impossible.