The usual standards of reporting apply. This rule, whatever your opinion on it, only applies in the case of unaccompanied minors and is as much for the protection of the male passenger as it is the child. I also think I'm correct in saying that it has been argued out many times in the past on PPrune. I wonder if this gentleman's stance would change, if it was his child that was travelling unaccompanied? As to how the steward dealt with it, that I can't comment on, having not been there. But there are definitely right and wrong ways of handling this highly awkward situation.
TSR2,
There are particular rows allocated to UM's, chosen specifically for their proximity to the galley and the crew.
F3G,
From what I read of the story, the wife refused to sit in the centre as she was pregnant and, apparently, gets more room in the window seat. Not quite sure how that works!