You'll all have to bear with me on this one...
The rule within a lot of airlines is that no single man (as in travelling alone) is allowed to sit immediately next to a UM (unaccompanied minor). The cabin crew have no choice in the matter, we must follow the rules set by our employer (unless we'd like a P45, of course).
The rule is mainly to protect the male passenger. Unfortunately, children sometimes lie. As an example: A few years back, I had a call from a manager asking what happened on a certain flight with a UM. I got a lot of questions. It turns out the child said my crew and I hadn't looked after the child and ignored him throughout the flight. This was (obviously) not true (I wouldn't be here otherwise). Basically, the child had wanted a teddy and sweets from the duty free trolley for free (as he was bored) and this was naturally declined. Therefore, he lied to his mother, who was the one complaining to the company. It got cleared up pretty quickly, thank goodness.
The above is one example as to how careful one must be when dealing with children. I would love for all kids to be little angels and all sweetness, but unfortunately that doesn't always happen.
I know that there are female abusers out there, but traditionally (for the lack of a better word), abusers tend to be majority male. Remember, kids read so much on the internet these days, that they may get "inspired". This whole thing is such a minefield, unfortunately.
I have to say that although I wasn't on the flight described in the DM article, it sounds like the situation wasn't handled very well by the crew member. One has to be very discreet in such situations, especially when having to move someone. I suspect this crew member will have received a b
ing from their manager (or worse). This crew member (by the sounds of it) hasn't understood the ruling properly. The passenger shouldn't have to move as he was travelling with his wife. Then again, we don't actually know what happened that day.
Gg