Why don't Hawaiians like the rest of us Americans.?

I was recently in Kauai and overall had a great trip. But noticed some hostility from the Hawaiians living on the island. At one point we were flipped the bird for no apparent reason by an opposing vehicle. If it's the fact there are so many tourists, I can see how that would get annoying, I grew up in a small tourist town and sometimes got overwhelming. But I've listened to some of the music and that seems to indicate that maybe there is a feeling of being overtaken, not being able to preserve the culture, etc. I am just trying to understand. I made some great friends from some of the other pacific islands when I was studying abroad in Australia a few years back and it would have been nice to have some fun interactions with those living in Hawaii while I was visiting. The nicest response we got was from Puka Dogs - the girls working there were great and loads of fun - interacting with all of the customers - thank you!! Everyone else just seemed happy to see us leave...