The Hawaiians don't like some of the mainlanders is because they don't keep their beaches clean. Another reason is because they don't respect their culture. This is the opinion of some of the Hawaiians, not all of them.
Think about it. You live in an island paradise that is being despoiled by development mainly due to tourists. Even though the state's economy depends on the mainlanders, how would you feel watching all the pristine beauty you love get polluted and go under the plow? Not hard to understand such feelings then, is it?
The same reason people in Florida do not like the seasonal snowbirds.
It is nice to live in a beautiful place, cut when you become inundated with tourists, who are generally ( speaking from my experiences and not always the case ), loud, boarish, cheap, and crowd the places that you like to go to, as well as not be respectful of the nature and litter etc. you tend to get annoyed.