I've seen some doozies in my time.
I've also had a QF flight MEL-SIN (just before they started the DXB hop instead) with a man proclaiming loudly to be an Aboriginal Elder (now i'm not a racist person, and of course you cannot necessarily tell someones ethnicity by the colour of their skin, but this guy was as white as I was). He then started ranting that no one would serve him a drink (actually, it all started with that, and him asking 'who do you have to root (not using that word, was harsher) to get a drink around here' whilst we were taxiing for take-off (it turns out the AFP denied him boarding the day before for being drunk, and whilst he was sober upon boarding, it was clear he did not wish to be; makes me wonder why they let him board really). I was in 80A, and he was in the row in front. I simply sat there with my headphones in, but not plugged in, and listened to it all unfold. He then started calling 'Qantas a pack of c***s' (yes, those exact words) and demanded to see the captain to be allowed to have a drink. He was accusing crew of being racist white c***s because they would not serve him a drink. On and on he went about being a lawyer, and was in some trash-tv show on pay tv (I never did find out if he was despite searching). He then said Qantas were 'white c***s abusing our land and i'll see to it that you c***s and your c***y company never fly over our cough****g land again'. Charming fellow. About 2-3 hours it went on, and the CSM handled this like an absolute pro. The crew were nothing short of amazing.