Okay, jokes aside, a mods job is to decide. To decide who is right and who is wrong in the context of the community. And we're not King Solomon so at least one participient will always feel he was deemed "wrong" and be unhappy. Even if there is no right or wrong side, no black and white. Most interpersonal communication is quite gray, even on the internet. And while it would be cool to instantly jump into a discussion when something offensive happens for the first time, it doesn't work that way. A mod probably comes in after sombebody else mentioned the thread as offensive, so the offenders are already 5-20 posts further along their path to a full blown flamewar. When we see something, we can say "hey, wait, don't do this again, or else...". But if that was 20 posts ago, I would feel pretty idiotic to say "hey, wait, don't do this another 15 times, or else...". Sometimes, the thread is too far gone to send a warning just like I wouldn't expect an officer to fire a warning shot if somebody killed 15 people and is aiming at #16.