Jagman, don't be sorry, you are spot on !! There are certain mistakes that are unforgivable, taking off on a taxiway in CAVOK where the lighting is so obviously different is one of them.
I always like to ask the " there by the grace of god go I " brigade if they'd feel the same way if their family was on board and the " little mistake " killed them all.
It's not friigin' McDonalds, people are trusting you with their lives !!