Sure, why not? Morality and law are not always aligned. I'm not sure I would go so far to consider these sorts of trade sanctions "immoral", but I wouldn't fault someone for believing so.

In this case, though, I think Huang just believed these sanctions were the wrong move, and would end up long-term helping China and hurting the US. Which is fair to believe, but believing a law is counterproductive doesn't give you immunity if you break it.

Can you make the case for trade sanctions being a moral issue?

Absolutely. Immoral and illegal/unlawful are separate things alogether.