While I think it’s true that a democratic China would be less concerned about the presence of democracies on its borders, the other two factors don’t ring true. It’s not clear why a democratic China would suddenly become less fearful of internal instability. Don’t all countries fear internal instability? A democratic China may provide more productive avenues for domestic grievances to be aired, but it’s not as if the end of single party rule would make subsequent regimes comfortable with massive internal instability (see: India). Second, the idea that a liberal democratic China would be “less prone to seek validation at home through the domination and subordination of others” is belied by, among other thing, America’s post Cold War foreign policy record.
Friedberg’s phrasing might make sense if the current Chinese government were unusually prone “to seek validation at home through the domination and subordination of others,” but the record of modern Chinese foreign policy is generally not one of pursuing a policy of dominating and subordinating other nations outside China’s borders. China has territorial disputes with many of its neighbors, but Beijing is mostly advancing territorial claims that the previous Nationalist government made. These claims are also some of the same ones made by the current democratic government of Taiwan. Obviously, Beijing is the one aggressively pressing these claims because it has the power to do so, but what would make a future democratic Chinese government any less interested in pressing the same claims just as aggressively, if not more so? A newly-democratic China would almost certainly be a strongly nationalist one, and nationalist democrats are not known for relinquishing claims to territory that they believe to be rightfully theirs. They are also quite capable of creating justifications to seize territory that is not rightfully theirs because they believe they have a mission or ideological license to do so.
The record of late 19th-century Britain or Meiji-era Japan ought to disabuse everyone of the notion that having a liberalizing and democratizing political system precludes the pursuit of an aggressive foreign policy. Rather than looking at America’s post-Cold War policies around the world, a more useful comparison might be with America’s early republican history as an expansionist power in North America. Early republican America was the most liberal and democratic country in the world by the start of the nineteenth century, but that hardly prevented it from using force or dominating other peoples. Increasingly democratic politics included expansionist goals that shaped U.S. relations with the rest of the continent. A democratizing China might or might not become more aggressive toward its neighbors than the current regime, but the assumption that a democratic China would be less aggressive in its dealings with other states in the region is a shaky one.