The problem with a lot of these campaign groups is that they need headlines - and so they reach for the big numbers and simplistic slogans to get journalistic attention. And they're often not too honest about how they do it.
It's depressing, but also depressingly successful. The stories write themselves, so it's easy cheap copy for the media - who rarely seem to concern themselves with anything like checking if ti's bollocks. Not helped by so many journalists being utterly crap at numbers.
Everyone should be forced to listen to Radio 4's More or Less.