Here's a question: has China done anything so far that violates UNCLOS or other international laws to which China is a signatory?
Note that I'm asking for actual things that China has done, not biased interpretations of China's claims and intentions.
First, the nine-dash-line. International law does not allow nations to claim open waters as sovereign territory. Nations can only have territorial waters based on sovereign land masses. The EEZ of a nation is not its sovereign territory, only an area where it has exclusive economic rights, mostly related to resource exploitation.
China has *never* claimed all the area within the dashed line as its sovereign territory. This is a myth repeated by anti-China media to confuse and mislead the public. The nine-dash-line denotes a region where the ISLANDS are sovereign Chinese territory, but the waters are still governed by UNCLOS designated regions of territorial water and EEZ.
Second, UNCLOS allows EEZ only around natural islands that can support human habitation. At first glance, this means artificial islands, like those reclaimed by China, are not eligible for EEZ. However, whether artificial or natural, China is still allowed to claim *territorial* waters around those islands, and that is exactly what China has done.
As for skirmishes between fishermen and maritime law enforcement, whether Chinese or from other nations, let's not forget that this area has been under dispute for well over half a century, probably even longer than that. The Chinese coastguard is arguably one of the more restrained actors in the area, especially compared to the likes of Philippines. If this situation is to change, then the relevant nations need to sit down together and work out a deal, like all other border disputes.