You seem to be the master of deescalation. Can you explain this interaction and what you said in a little more detail? We could probably all learn from it.
The sentence he highlighted was this one:
One guy got defensive but, because I didn't get angry back, cooperated.
I might disappoint CC a little because I was so moving so fast that my memory of what I said is somewhat of a blur. What I do remember clearly was that the attitude that I take in these situations is that the people I'm asking for a favor owe me nothing. They are doing a favor, and I am the supplicant. So I don't get on my high horse and come off as someone who feels entitled. There's a very good reason I don't sound like someone who's entitled: I don't think I'm entitled. It would be nice for them to do what I'm asking, and it would probably cost them very little whereas my gain would be great, but that's for them to decide.
Back to the United incident. Once I explained that my plane would leave in about 12 minutes from a different wing of the airport, the guy said, with a tone, "The door isn't even open yet." I answered, "Yes, sir, I understand but I'm trying to get as close to the door as possible when it does open." He seemed to get it because he said, "Oh, alright" and stepped back into his seat to let me pass. [These are my rough recollections. I could be off a little.]
My attitude that has worked for me from about age 30 on can be summarized as "Keep your eye on the prize." Someone on Facebook recently asked what one line of advice people would give someone about living his/her life. I answered, "In any conflict or issue of controversy, keep forefront in your mind what goal you want to achieve." What that will typically mean is that you don't escalate, you probably ignore insults, you let people save face when they back down, when they give you even some of what you want you thank them, and you don't gloat when you win, to name five.