Just to be clear, I would not support starting a war with China "just because we feel like having a war" either.
However, it doesn't really take a lot of research to see that the Red Army faction of China's government is quite aggressive, and that there is a strong desire, backed up by long-term efforts at increasing their military capabilities and regional "presence", at replacing the USA as the dominant power in Asia and the Pacific. It seems very likely that they're going to put us to the test at some point, by means of invading Taiwan or some other US ally or protectorate, as a means of testing our resolve while at the same time (they hope) demonstrating to all of Asia and the Pacific (if we back down or they beat us) that there's a new Big Boss in the region... and that everyone had better kowtow and play along if they know what is good for them.
It is my opinion that letting them get away with it, to avoid war, would ultimately be a bad idea. It is almost certain they would not stop there. While they might not invade Australia or Japan, their long-term goals almost certainly include making them client-states who listen carefully to what the new Big Asia Boss wants and do what they're told.
The Aussies have always been good allies to the US. I would not willingly leave them swinging in the breeze to face a rising Red Chinese Empire alone. Also, Japan is dependent on us for protection to a large degree... part of the price for demilitarizing their society after WW2. We can't just walk away from that half of the globe and leave it to China.