The statue they are kneeling in front of is King Kamehameha.
He was a violent conqueror who, after obtaining superior firepower, savagely attacked defenseless natives on the smaller islands of what we now call Hawaii. We don't know a lot of details about Kamehameha's violent campaigns - since less developed societies did not write as much down as, say, Christopher Columbus or Thomas Jefferson - but we can assume that he, as a king and conqueror, oversaw mass enslavement, rape and torture.
We do know that he ritually sacrificed those who opposed him, like his Oahu rival Kalanikūpule and many of his warriors.
After "unifying" Hawaii, Kamehameha instituted laws, reforms, opened trade, and so forth. But there's no doubt that his kingdom was built on blood. His office as "king" is one that should repulse progressives. America figured out that was a bad idea 250 years ago and got rid of kings (thanks in part to Thomas Jefferson).