I don't really have anything to say on the specific value of the cap Cameron is proposing. I lack the necessary data for that. I would, however, like to point out three things:
- Arguing that the cap can't be too low because lots of people want it to be lower still is functionally equivalent to saying "A lot of pricks want me to be a bigger prick, so I don't see why my prickishness should be a problem" ;
- Telling people that in a time of high employment the cause of child suffering he's focusing on is the people who could work but can't be bothered displays an ear so shot through with tin it belongs down a mine in Poldark;
- How can a man with four children possibly be so stupid as to sign on to arguments that suggest people view an extra baby or nine as being a good way of avoiding hard work, or ensuring a greater amount of living space?
Working title: "Rugtwats".
 I wonder if Enoch Powell ever tried that one? "A lot of people wanted me to say 'The river Tiber foaming with much blood, and also the piss of darkies and the semen of homos'!"