Trade helps people and is a powerful motivatove because it creates wealth. We are putting a condition on them becoming wealthy by saying you must become a democracy and respect human rights before we will trade with you. That helps everyone because it spreads human rights, it spreads democracy, and it takes that most basic of human desires (the desire for money) and says "if you want it you must protect human rights and honor democracy". That does more for the people living in dictatorships then a hundred years of our current policy of giving the dictators everything they want and requiring them to do nothing.
Right, the magical sanctions fairy will just instantaneously turn the PRC into a liberal democracy with strong environmental and labor laws.
Comment