The world is of course actually messy and not b&w, but that fact doesn't change that.
It's like saying that killing is wrong, but sometimes we still have to kill. Yes we do, and killing is still wrong. If you kill someone, it's not because "humans are messy". Oh humans are just imperfect and sometmes you just kill your neighbor, it just happens, no way to avoid it. If you actually want to get anything done you can't be so aspberger absolutist and figure out how to work WITH the neighbor killers.