A rule was broken. Most agree with that. The question is what to do about it. Had it been intentional and had it had a definitive impact on the outcome of the fight then I would be all for making this a NC, suspending GSP and taking away his winnings. However, I see this as no different from an accidental groin kick or eye poke. It's against the rules and in most cases unintentional. So, the outcome of the fight should stand and moving forward new rules are applied to ensure no more accidental lubing. That is all...
We do not know if it was intentional or not...
This is much different than and eye poke or groin strike. Those are very easy to accidentally do.
There is no excuse for having lube applied to your neck,back and chest of all places. Much like there is no excuse for steroids.
Remember that greasing is a highly effective form of cheating. Much like steroids.
Because this may or may not have been accidental, I say it is fair to leave the fight the way it stands as a win for GSP, but
I do think GSP should at least be fined and suspended. That seems fair. Rules are Rules.
This is one of the rules where accidents don't excuse the action.