They are growing their military forces to gain political leverage in East Asia and then the world. They support anything that destabilizes the west thus their support of Russia, Iran, Korea, Vietnam. Their history of communism juxtaposed to democracy. Their form of capitalism which is not based on a free and fair economy. Ignoring international waters and borders. A bad actor.
The Chinese government's rampant greed is threatening all of its neighbours. As you can see in the latest disputes over the Spratly Islands in the South China Sea, China does not deter from taking drastic measures(putting an oil rig in disputed waters and ramming Vietnamese ships). Concerning the disputed islands, I see that there is no clear proof whom they belong to. Nevertheless China should not be provokative and keep the status quo. But its voraciousness goes beyond its sense of peace.
The rise of the Chinese military and its increasing defense budget, cyberwarfare, anti-satellite technology, etc represent a direct challenge to the current world order. If China decides to invade a disputed territory that belongs to a long list of US allies as it has been acting as the neighborhood/regional bully, then by treaties we would be required to declare war against the PRC which would be disastrous for global markets and the two superpowers.
Since WW2, the US has had considerable military and economic influence over the East Asian region. With the rise of China and its growing military, we should be seeing this as a threat. It is not a short term threat, like North Korea, but is something that we should be watching over a period of time. In time, China will be a threat to all our allies, starting off with Japan, then India, then Taiwan, and finally Vietnam, the Philippines, and South Korea. China has also been propping up Iran and North Korea, and this could shift the balance of power completely, causing political instability in the region.
I think that the rise of China's military power is a threat to East Asian stability because China can be an unstable country. They are also a country that wants to amass an extraordinary amount of power. I believe that China will use its military power not for defense, but to overpower its neighbors.
The United States of America is the country who should be threatened because we owe China BILLIONS of dollars. It is known that China has taken on much of America's debt. That is the reason behind Obama allowing the leader of China to stand beside him at important events. We should be threatened by their military power's rise because we are the one they will target if we do not start repaying our debt.
If China was more independent, I think there would be an issue, but since the United States plays a big role in how well the Chinese economy is, I don't see them being much of a threat. Every country knows that if they start any kind of military problems, the United States will step in. This much has been proven time and time again throughout the course of history.
China knows that we wouldn't want to go to war with them, but if they were to start invading countries we would have to. Plus many other nations around the world would also get involved. I also believe China knows that they are dependent on the United States and all of Europe to maintain their economy. If China started major trouble or invading countries they would loose all of their exports and their economy would eventually collapse. Thus not being able to support a huge military. If we are concerned about this buy less goods made in China and they wouldn't have as much money to build a huge military.