If politicians see the public and the media angrily demanding severe punishment for such a group, then they will do whatever it takes to make those people suffer.
As he points out, it's difficult to argue the applicability of this rule to asylum seekers. But there is a group who seem to skate. They've profited at direct cost to the taxpayer for actions that, although legal, were unquestionably ill-judged and arguably immoral. In their defence, they can only say that, "everybody else was doing it" and, "it wasn't against the rules". The public and the media have indeed angrily demanded severe punishment for them. But every time this has been discussed, both parties have reluctantly declined to make the finance industry suffer: we've had promises to "look in to" bonuses which are "unreasonable"; the statesman-like decision not to impose windfall taxes on bonuses has reluctantly been taken; radical reforms such as Tobin taxes have been carefully reviewed, then shelved.
All of these decisions may well have been the right ones - that is to say, proportionate, just, and unswayed by popular sentiment. It's simply curious that the political gravity which now demands that MPs pay back excessive gardening bills doesn't pull so strongly when the potential scapegoats are the high-flyers of the financial industry. There's a certain logic to this from opposition: if he'd spent time calling for penalties on bankers, how could Cameron appear at conference and say that "too much government" is to blame for the financial crisis? But from the government's perspective, there's just as much naked political value to be had from keeping the public's attention focused on the bankers' role in getting us all here. Instead, all discussion of that seems to be off the table. Even as Lloyds is calling for another £5bn from the government as part of a scheme to avoid paying for toxic asset insurance delivered by that same government.
There's obviously some downside to calling for the heads of bankers, in a way that there isn't for venal MPs. But what?