The letter is clearly a bit of a show-off; the client is probably someone whose business, or connections, the letter-writer wants (or maybe a pro-bono), and isn't being billed for even half of the time it took to research and write that letter.
I didn't get that impression at all. By the attorney's own comments, the client is just a run-of-the-mill joe who had a problem with the Hyundai dealer and decided to go public when the shit hit the fan.
No, I think the attorney's sole reason for writing the letter was to illustrate to the law firm that had been retained by the Hyundai dealer that they didn't know what the **** they were talking about (from a legal perspective). He "compliments" the attorney for that incompetence right at the beginning of the letter.
And the other purpose of the letter was to further illustrate that if the other law firm persisted in continuing the fight, that there would be repercussions far beyond merely defending oneself.
I think the attorney who wrote the letter simply enjoys being legally correct. And he likes taking the Bad Guy down in the same manner as Robin Hood takes down the Sheriff of Nottingham. I don't see that as smarmy -- I see it as being willing to pick up the gauntlet when it's been thrown to the ground.