Of course when an accident like this, it is unfortunate, and it adds a stink to the presence of US bases on Okinawa. But accidents of that kind also happen between Japanese and Japanese. In the end of the day, humans are humans, and accidents happen. Same goes with criminal behavior. Reality is that there are some nutjub anti-base people too such as this fellow and his group that block roads to get cars driven by Americans to stop and to bang the car and shout at them to die. Whether or not a Japanese is against the bases, that is not Japanese cultural behavior.
Anti-base sentiment on Okinawa is fairly high. But it does need a closer look. Some that are against the US base are against it because they feel it is unfair that about half of total US personnel stationed in Japan are in Okinawa. So there is a US base that is closing down called Futenma and the US plans a replacement for the base on a different part of Okinawa called Henoko. So some people are just against the US relocating within Okinawa. They just want less presence on Okinawa and for other parts of Japan to handle more. Granted there's still a sizable amount that are just simply against the US-Japan alliance but it is still just a subset that is anti-base. In some ways, it is understandable that they wouldn't always want a large US presence on Okinawa, but Okinawa's strategic location isn't going to change. That's why the plan is for Futenma to relocate to Henoko rather than someplace off of Okinawa and someone else further up in one of the 4 main Japanese islands.
In any case, the proportion of anti-base to not anti-base shouldn't be exaggerated. There was an election for the House of Representatives so of course, Okinawa districts were part of the elections.
Here is an image of all the districts in all the prefectures that voted. Overall, the Liberal Democratic Party of Shinzo Abe won big. In the picture below, they are represented as red. Green were parties that are in opposition to the LDP but still support some of the same things as the LDP such as changing the constitution or the US-Japan alliance. The blue are opposition parties that are generally also against changing the constitution and typically are also against the US-Japan alliance and the defense related laws that were passed 2 years ago. I added the names of some prefectures in English to the image.
http://www.sankei.com/politics/election2017.html
So then, let's take a closer look at the election results in the 4 districts in Okinawa.
http://www.sankei.com/politics/election2017/candidate/senkyoku-47.html
While candidates of course vary in positions and of party affiliation or independent, simply put, I will list their popular vote count along with their basic stance as either "pro-base" or "anti-base". So this is what we have for each of the districts:
District one
60,605 anti win
54,468 pro
34,215 pro
2,594 pro
District two
92,143 anti win
64,193 pro
District three
95,517 anti win
66,527 pro
3,031 pro
District four
82,199 pro win
75,887 anti
4,650 pro
So 3 are against and one is for. But if taking a total count of the votes, it comes to:
Anti = 324,152
Pro = 312,877
So its a very slight majority that voted for someone that is against the US bases. Now, among those that are against the US bases, the candidate that won in district three said that he wanted the Japanese Self-Defense Force to fill in where the US bases are. Well, I would prefer more support in Okinawa for the US bases, but this does show that the anti-base sentiment is not even close to "entirely against" as some posters here seem to think.
One other thing, about ideas about referendums for Okinawa independence, here is a survey conducted in Okinawa on April 22nd and April 23rd that included that question.
http://www.asahi.com/articles/ASK4S45G6K4SUZPS003.html
And the question:
沖縄県の今後についてうかがいます。あなたは、沖縄県はどのような自治のあり方を目指すのがよいと思いますか。(択一)
今の沖縄県のままでよい35▽より強い権限を持つ特別な自治体になる51▽日本から独立する4
Which goes as:
Next is about Okinawa Prefecture from no on will be inquired. What kind of governance do you think would be good for Okinawa Prefecture to aim for?
Okinawa Prefecture as of now is good 35%
A special governing body with greater authority 51%
Independence from Japan 4%
So when was the last time Tibet or Xinjiang held an election or had a political survey asking about independence?