Well, I don't often disagree with you Hamish, but.....
I think Nakamura was way out of line. The incident wasn't a 2 or 3 second lapse in the way Jacob excuses it, and it wasn't the same as the incident John Shaw mentions (I was right next to John when that one happened) as his opponent in that game immediately accepted that his 'j'adoube' was wrong.
It's hard to tell without the audio, but I don't think Aronian would have reacted like that if Nakamura wasn't trying to somehow avoid his responsibilities?! Nakamura also has previous - plus his behaviour after the game was awful.
Yes, they are playing for the highest stakes, which magnifies errors (including errors of judgement) but I find it difficult to believe he wasn't hoping he could get away with it.
Just my personal view, of course.
Also, I have touched the wrong piece on several occasions in my chess 'career' - not once did it occur to me to say 'j'adoube', it doesn't even enter my head. It's the most basic rule of chess and chess etiquette we learn when we start out in the game.