The thing is that China is not predictable. Take this 'X-men' stuff for example:
http://www.reuters.com/article/2012/05/ ... 7Y20120523Then there is what seems to be a nationist movement behind the islands disputes in the SCS and disputed claims with Japan:
http://news.xinhuanet.com/english/china ... 181518.htmSo what is of concern is the question as to just how much the government is really in control. It seems that the nationism that the government has been fostering for the last decade or so, as a replacement for the communist ideology, is taking on a life of it's own. This is particularly so since nationalism is the means the establishment is using to side step social inequility issues associated with the more to authoritarian capitalism.
So, the fear is that nationalist sentiment will force the government's hand and lead to rash actions. Where it the case that the central government was clearly in firm control, by soft means of widely accepted legitimacy and law and order (a pluralist system, possible democratic, would be the obvious solution), then I doubt there would be so much concern about Chinese miliarty expansion.
Let me offer some historical examples to illustrate the sort of thing we are all worried about:
http://en.wikipedia.org/wiki/Charles_X_of_FranceThis fellow ws the ruler of France in the 1820's. When faced with social unrest at home, he decided to start a foregin war to divert attention from the failings of his regime. So he invaded Algeria. The war didn't go as well as he hoped and he was overthown in a revolution in 1830 (the July revolution).
A later French ruler was also to se war as a way of diverting the attention of the people from domestic problems. It also failed (this time with a resounding military defeat too):
http://en.wikipedia.org/wiki/Franco-Prussian_WarSo, we see China laying claim to the territory of other nations, beligerently provocting a crisis and then trying to bully the other nation into making territoral concessions, all to the chears and cries of the nationalist peanut gallery. So far the CCP has been lucky and this exercising of Chinese national pride has served it's purpose, but sooner or later it will lead to trouble.
I will reiterate the point that it is not China's military modernisation that is at the heart of other nations' concerners but rather what is clearly an unstablity domestic situation and the irresponsible way the Chinese political establishment has been trying to handle that instability by progecting it outwards. Therefor, the conbcerns of neighbouring countries and their allies are well founded.