Disclaimer... Not seen it yet...
However, if the Batman was drawn from the Dark Knight Returns/ All Star Batman and Robin model... He's a horrible person who has indeed lost all/most his humanity. So maybe that explains the whole knuckles and killing bit.
Still and all, I like my heros to be heroes in general. Frank Miller did me no favors.
I actually like the version of Batman in the Dark Knight Returns... But not the followup books or All Star, where he gets more and more ridiculous.
Dawn of Justice Batman is like the Dark Knight Returns Batman but more violent and a killer. He's not as ***holish as the All Star one though.