How to share a mutual friend with an enemy
There is an old saying: "The friend of my friend is my friend; the friend of my enemy is my enemy." But what if one of your friends is friends with someone you preceive to be "an enemy?"
Do you disown the friend? Or do you make peace with the enemy? Or can you maintain a position of complete neutrality on the issue of this uncomfortable alliance between a friend and someone who is not a friend?
I've found myself in an analogous position, when two friends of mine had a falling out, and one of them accused me of betrayal when I wanted to remain friends with both. It's not a good idea to require a choice, especially when the complete facts about the falling out are not well known.
The same thing happens in the relations between nations. Taiwan and China are not friends. Each has claims to being the true government of the Chinese people. Each, in theory, maintains that the other is illegitimate. In order to recognize the current government of mainland China, the United States severed diplomatic relations with Taiwan. But Taiwan is a friend of the United States, and China is a country that the United States wants as an ally.
Sometimes, the best policy is to wait and see. We can't dictate to others who their friends will be. But if there is a real reason for an enmity, then eventually the truth will emerge, and there will be realignments. There's always the possibility that the enmity you preceive is due to a misunderstanding, and, in that case, you might be the one to change your mind. But if your perception of the situation is more accurate than your friend's, your friend may decide to back you up in case of a war.
Despite the severed relations between Taiwan and the United States, China knows that if it attacks Taiwan, the United States will not stand by and let it happen.