I might have disagreed with you, but then I thought of my own experiences.
I saw something that excited me. It was new, it was different, it intrigued me and I enjoyed it.
But then I didn't want the same again, I wanted more, I wanted better, I wanted harder, I wanted more excitement!
... just went back to the library and got another book out.
(I would have put a FAIL icon on this, but that might have given it away)
How did you know that your colleague didn't have these interests before? How do you know it was a "progression"? How do you know it was "caused" by the porn?
You seem to be saying that, just like the idiots who proposed and passed this law, *everyone* cannot be trusted not to go out and commit murder or shag animals or abuse children just because they look at this stuff.
And if you want some evidence of how wrong you are, I suggest you look at the work of Professor Milton Diamond PhD of the University of Hawai'i who studied the effects of the availability of porn (including "extreme" porn) in the USA and Japan and concluded:
"It is certainly clear from the data reviewed, and the new data and analysis presented, that a massive increase in available pornography in Japan, the United States and elsewhere has been correlated with a dramatic decrease in sexual crimes"