This week, a 36-year-old Welsh rock singer called Ian Watkins from the band Lostprophets – no, I had never heard of them either - pleaded guilty to 13 sexual offences, including two of attempting to rape a baby. The prosecuting barrister told the court that the two women standing beside him in the dock had also "sexually abused their own children and made them available to Watkins for him to abuse." Watkins had sent a text to one of the women: "If you belong to me, so does your baby."

Now, I have no interest in trying to enter into some sort of crass competition over outrage. Or, at least, I wish I didn't. For there is a part of me that now wants to write something like this: "Ian Watkins is a walking advertisement for the death penalty." But, the thing is, I don't believe in the death penalty. Thinking about this level of evil it is easy to be lost for words.

I do not resile from the force of the word evil. Yet there is a problem with it – because of its metaphysical implications, it suggests evil as something alien and other, something of which we are possessed, something that takes us over.

This, of course, is a staple of the horror movie genre. But the problem here is that we can too easily think of evil as something outside of ourselves. And this is convenient because it absolves us of the deeply unpleasant task of recognising that the Ian Watkinses of this world are precisely that: of this world.

We reach for a term like evil because it also allows us to say that we do not understand. And we want not to understand for two reasons: first, because understanding sounds a little too much like forgiveness or even some sort of sympathy or endorsement (which, emphatically, it is not); and second, because understanding evil as something human locates it dangerously close to me as a fellow human being.

Part of the reason we compete over outrage is that we want to signal that this sort of behaviour has nothing to do with us, with me. It is a way of banishing someone from the human family – hence the death penalty. That is why we sometimes call this sort of behaviour inhuman.

But nonetheless, I really still don't understand. Being sexually attracted to young teenagers is wrong. But being sexually attracted to babies is incomprehensible. Maybe, however, we are looking at it upside down if we think of it as primarily a sexual thing. This idea helped me. "Perversion," argues Robert Stoller in a book of the same name, "is the erotic form of hatred … the hostility in perversion takes the form of a fantasy of revenge … [that] serves to convert childhood trauma into adult triumph." Or, to put in another way: "There are those who fuck from desire," wrote the (himself highly problematic) psychoanalyst Masud Khan, "and those who fuck from intent. The latter are perverts. Because intent, by definition, implies the exercise of will and power to achieve its ends, whereas desire implies mutuality and reciprocity for its gratification."

So maybe – tentatively – something like this: paedophilia is not about sex per se, but sex as control. For the most part, having desire is about being out of control. Of not having power over the object of our desire. Some of those for whom this out-of-control-ness is intolerable seek an object of their "sexual" attention that is entirely within their control. Hence babies. Maybe, then, we find the idea of sexual attraction towards babies unimaginable because we are thinking about it the wrong way round. Its not a pathology of sex, it's a pathology of power.

Twitter: @giles_fraser