Every time I didn't offload- I regretted it.
I explain to the passenger the situation, that I understand why they are frustrated but that because of X i must do Y. I give them the options and explain what will happen if they do not comply. Any sign of aggression- they are off. I do not get paid enough, and passengers do not pay enough, to be abused and intimated by a fellow passenger who decides it's their right to kick off and abuse evrybody else. 9 times out of 10 the passenger apologises, explains they've had a bad day, and sits down not to be heard from for the rest of the flight. the other 1 time, is when they're offloaded and then proceed to kick off in the terminal.
I learnt the hard way that the times you don't offload are the times you wish you did. Ten times better for them to be left behind kicking and screaming... than to be kicking and screaming at US at 30, 000ft!!!!!!!!!!!!!