The elves and drow hate eachother, so this is to be expected. Other than this strange remark, Kivan is always empathising with and urging the PC to emancipate captives. I am not terribly learned on any of the races cultures, but I don't think the elves keep slaves or look down on them more than they do any other non-elf. Finally, Kivan comes from the elven equivalent of a working class or peasant background, so he doesn't seem like someone who would be terribly snooty and judgemental towards his social "lessers".