Asking for an example is ill-posed, given that democracies are rather young constructs compared to the wider human history. Mind you, I am rooting for Taiwan, but I would expect something like what happened in Hong Kong rather than all-out war if the USA rug pulls Taiwan when it comes to support.
Europe has already signaled that they won't do anything when it comes to Taiwan.
What example do you know of a democratic country collectively "accepting" invasion by a dictatorship because being free is "not worth it"?
I can't really come up with anything.