You're unreasonable to link to a DM article that's for sure. A DM article that is just a re-hash of a piece Marina Fogle wrote for The Times.
The tl;dr and not clicking on the Fail version is: someone, apparently a neighbour, reported they were shouting at their children. Social services came by to speak to them about the concerns. The Fogles provided proof they were on holiday at the time so not even there. Social services closed the case. Malicious complaints happen.