I just want to stress that all we have is the passengers' side of the story. So what was actually said in terms of specific wording, and more importantly, the tone of the conversation, is really not 100% known. And again, I assume that the passengers are trying to make themselves look good so we are getting their version of the story in such a way as to make them look "in the right" even though many of us feel that they failed to do so.
And I said this before but I feel compelled to say it again. There must be some kind of procedure for removing a passenger from a plane that goes beyond the FA just making a snap decision on her own. It's got to be more than the FA being in a bad mood and taking it out on the first passenger to make a comment that strikes her the wrong way.
Something the passenger said or did was provocative enough for the FA to take it to the next level and whatever that something was may not be readily apparent from the passengers' stories.