Accepting Taiwan as a "state" would be to give legitimacy to any separatist group that decided it wanted out of an existing nation. You would then have to grant legitimacy to Chechnya, the Tamils, the Kurds in Iraq, etc. How would we have felt if the world had decided to recognize the Confederacy during our own Civil War? We should stop protecting Taiwan and let it be returned to China, where it rightfully belongs.
Do I have that right -- we should stop protecting a democratic country, and let it be swallowed up by an oppressive dictatorship, because the democratic country, resumably including the country's citizens, "belongs" to the dictatorial one?
Any vision of international "property" that goes that far, it seems to me, is not one that we ought to respect. (I set aside the question whether sometimes we have to reluctantly accept it, since resisting it may involve more blood and treasure than we're willing to spend.)