Because in 2003 when this article was published the attitude towards images of CSA was very different, you can tell that from the language used “child porn.”
The bulk of the article is written in a humorous/satirical manner and seems to be pointing out (in his view) the ludicrousness that viewing such images may not necessarily be a crime if you had a good reason to view them or it was an accident, essentially that we were creating thought crime.
It was a very common view amongst left wing men, I know this as I argued with enough of them. There were arguments about the criminalisation of watching porn involving teenagers over the age of consent but still classed as minors. That artwork or innocent pictures of babies in the bath could be classed as “child porn”
There were also free speech and freedom of the press arguments from the libertarians.
The view point of pedophilia being a sexual orientation was still hanging around and it was unfair to criminalise people for something that they couldn’t help. Viewing images was considered to be a passive act.
It was a very different time and I am grateful that we are more enlightened now and attitudes have changed. But I will not condemn someone for writing what was not an uncommon view point at that time.
I doubt very much i read the article at the time of publication as I considered Liddle to be leftie rage bait and read little of his work. Although I did occasionally smirk at his jabs at the hypocrisy of the left.