I have ever only experienced extreme rudeness/unacceptable behaviour on two flights in all my many years of frequent flying.
One was on Iberia, when I went into the galley in the middle of the night on a transatlantic to get some water and two of the attendants were smoking. I was threatened with physical violence if I reported the matter which I did. I'm still around and wasn't 'done over' by anyone on arrival in Madrid as they had threatened!
The other was under the same circumstances when a very rude arrogant FA refused me a bottle of water (I was in Business class on a flight from BKK, not that class of service should make a difference), and was most unpleasant in his refusal. He accused me of 'having a problem with German people' (I don't and even if I did it's irrelevant) and I reported him to the CSD who dealt with it sensitively and appropriately. I also got a number of Miles credited.