The first is that the announcement itself, and the details of the change, have been botched by insufficient care and preparation. The answers to some obvious questions - for instance the position of two-income households - hadn't been fully thought through, and nobody from the core team was prepared to speak to the media when these issues were raised. I think this is indicative of the current attitude among Ministers: they have underestimated the complexity and importance of public office, and thus approach it in a slap-dash way. This is very dangerous in the long term, like operating a massive machine as if it were a big joke.
The second is that middle class people act like they were betrayed. They are making the same mistake that people did when they voted for Thatcher. They think in a world of 'Us and Them' rich Tories look on a middle class person as 'One of Us'. They do not. They will not look after you. For example, they are happy for the number of white collar jobs in this country to fall quite far. Their economic interests are not tied to preserving the size and current composition of the British middle class.
Of course this current measure does not hurt the middle classes very badly. It's like a little slap. But the slapped person is looking bewildered 'I thought we were friends!'. No.