It's one reason why many humans refuse to be allies with the Sangheili. The other thing to note though is that even though he slaughtered so many humans, he is the only reason humanity even survived the war. Not only that, but he's gone on to become our greatest, and arguably only ally in the post-war era. The thing that disturbs/interests me though is that due to Sangheili culture, war and combat is a normal thing for every member of their race. So after the Covenant War ended, many of the Elites who did not want to continue the fighting don't feel guilt or remorse for what they did to humanity. Arbiter included seemingly.