He's a killer and he likes it, just like the other CP-0 (and 9) agents (except Stussy maybe). I guess he's more of a fighting man, since he was loving his battle with Zoro up until he was cut down and even wanted to uncuff him from Sogeking, but he was in Mary Geoise justifying Charlos' actions against Shirahoshi.
He ain't giving up his carte blanche to kill, even if he has to support something as deplorable as slavery.