Mr. Perplexed
Do you have any sort of background in customer service? My limited experience has taught me that some people simply have the 'wrong attitude' towards people who are there to provide a service. It is not necessary to use profanity or a physical threat in order to cause concern. It is a case of the 'Here we go...' scenario, when you just know this is going to be one of those awkward customers.
It is quite a threatening situation to be in, especially, I expect, if facing the prospect of being locked in an aluminium tube with this person for 8 hours. If in doubt, removing a passenger should be FA's perogative. Any manager worth his salt would always back up his staff and ask questions later, even if they are being heavy handed.
Moral of story: Don't p!ss the flight attendants off any more than you would p!ss the captain off. To a passenger, they are essentially one in the same.
Pie