Moral Event Horizon

There is a phrase of Iain M Banks of which I am becoming increasingly fond. He often talks of the moral event horizon but I’ve never seen him define the term.

 I’ve been thinking about this, this morning, in the context of if and how one chooses to engage in political activity within or without a system that is flawed (and perhaps deliberately so).

 For me the moral event horizon is where you reach a situation where it is impossible to act morally, where all the available means are to some extent immoral. A little deeper in and there is the situation where all of the ends are to some extent immoral.

  How would you define the moral event horizon?

 I’d be interested to hear anyone’s views.