This goes far beyond the "9 dashed lines" dispute. VN nationalists are pissed off at PRC for pushing PH running to the Hague.
Per the Hague's ruling, the "above water features", including the largest Taiping (Itu Aba) island in the disputed area are "rocks" ineligible for EEZ (1). This effectively means all extended EEZ claims based on little islands, from all parties including China, Philippines, Vietnam, Malaysia, Indonesia, and Brunei are invalidated.
While the Hague's ruling did not take a stance on actual sovereignty of various islands, the purpose of taking possession of them in the first place is to stake a claim on the EEZ. Vietnam spent considerable resources in taking and holding the islands for many decades, and their efforts are now spilled soup.
To add salt to injury, while the Philippines has been granted EEZ based from Palawan, the Hague determined that Chinese fishermen have traditional fishing rights within PH EEZ (around Scarborough Shoal area), but not Vietnamese fishermen.
In future, the Hague's ruling will also have negative impact on Japan's Okinotorishima EEZ claim of 400,000 sq km ocean area East of Philippines, should Manila (or anyone else) decides to take them to the Hague.
(1)
http://www.taipeitimes.com/News/front/archives/2016/07/13/2003650919