I don't think anyone sensible would fault China for taking advantage of something that is advantageous for their businesses, nor for them to advocate for it. It would be irrational for them not to, the subsidies exist so obviously any reasonable business would use them.

Nonetheless, it's clearly not in the interest of US businesses. The US is not obligated to provide subsidies that, due to the scale of trade using this tool, demonstrably favor Chinese small businesses over those in the US and distort the market.

I'd much rather see the market made more balanced by charging the same prices for shipping than by tariffs. At least that's a real cost. Though I have the ulterior motive of thinking charging full price for air freight will reduce carbon emissions and inefficient supply chains.