Saying that Taiwan is merely a nationalism and internal unity issue, and that people's views are merely a result of propaganda, ignores the very history of how Taiwan came to be and how the Chinese civil war developed. Your take also ignores the fact that unification is Chinese core value, which is valued more than western freedom of speech, and that this core value has been around for thousands of years.

But more importantly, you dodged the military strategic significance of Taiwan. Telling China to give up Taiwan is like asking China to give cut off its lifeline.

At the end of the day, your point boils down to that China ought not to think that way, for reasons that you believe are the only legitimate reasons. But that is useless: Chinese do view things that way, and if foreign forces pressure China to let Taiwan go, then they will fight to the end.