Do you really think most educated people in PRC don't know about 1989? They know, they just think it would be deeply unreasonable to raise this kind of controversy in public when the government is making the average Chinese's lives so much better. It's a very complicated game, and there are multiple sides pushing opposition underground.

Opposition to the Iraq war was a very similar story, where many and perhaps most people were hopeful that promoting democratic values in the Middle East would actually work, and nip the root causes of Islamofascist terrorism in the bud. Of course the reality was very different.