I don't think you get to abdicate responsibilty of some avoidable negative externality of something you do just because some entirely separate function of it is the thing your customers want. If I were a plumber who fixed leaks by diverting the water into the customers' neighbors houses, my customers aren't the ones responsible for the damage it causes. I don't think it matters even if the externality isn't avoidable. I think people who sell murder-for-hire services are culpable of murder, even if they are paid by someone else
If the argument were about slavery instead - slavery enables cheaper goods, ergo by buying our products, some of which were made using slavery, but we refuse to reveal which ones, but nonetheless by buying them you support slavery and are morally responsible for the slavery not us. Nobody would accept this framing.
I agree that China has done very well from manufacturing and trade, and would not have done as well if they had not industrialised at a large scale. But that doesn't change the fact that industrialisation of this kind causes pollution and is damaging the planet and it especially doesn't mean that China has no moral obligation to do as much as it can to reduce emissions.
I also don't believe the argument that the pollution is inherent to production, or that there is no way to satisfy demand without pollution. (or that china, specifically, derserves to be the one to profit from satisfying that demand). Production of almost all commodities can be done without massive emissions these days, and even when it couldn't, nobody was forced to ramp up production
Someone will inevitably jump in here to point out that china makes a lot of solar or whatever. Sure, they do. They also make a lot of wind power. Their emissions per capita are trending in the wrong direction though. Europe's have been going DOWN since the 1970s, and china's are going UP. China's emissions per capita are roughly equal with the EU at the moment and are going up - pretty soon they will catch up and surpass the US.