You shouldn't mix the internal policy and international politics

Those two should be dealt with separately. Chinese mistakenly think a good government should behave towards other countries, therefore US is bad because it is oppressive to other nations. But the truth is the complete opposite, US government is democratic inward, therefore it treats its citizen the best. Internationally, its top priority is to protect US interest, the rest are all secondary.

Chinese government is very generous to all other nations but treats its own people like dirt. That is a recipe for failure, whether it is democracy or autocracy wouldn't even matter.

As to what happened in the past, you need to think progressively. There were dark ages all around the world, but things have improved dramatically. There is no point holding on to grudges in the past. Take Scotland as example, there were wars between England and Scotland 300 years ago, but now people of Scotland choose to stay together with England.