having a "right" to do something, doesn't equate to that something being the proper, civil, or moral thing to do. It certainly doesn't prevent people from getting angry (maybe justifiably) at you excersizing your "rights".
The person didn't threaten to do anything. He equated your actual threats to a hypothetical threat, that had he made, you would be angry about.
I respect people being aggressive about getting refunds, and price breaks, etc. - even when they are technically or contractually wrong, but IMHO you were the one that crossed the bad behaviour line first.
It sounds like they made some effort to meet you in the middle - sometimes you just have to know when to quit and accept the rest as your responsibility and move on.
"Customer Service" doesn't mean "punching bag". You need to remain civil and give people an opportunity to help, while allowing them to save some face and feel like a human being.
By the way, you remind me of my wife, who is the queen of getting what she wants. I have this same conversation with her sometimes when she gets a little to mean-spirited with people. I do appreciate the money she is able to squeeze back into my checking account by being aggressive, persistent, and diligent though
Just my .02