I can see why this board would be better without people posting porn all over, but it was just in the background on his computer screen (and it wasn't a particularly distasteful picture either, and probably just barely qualifies as porn) and I would have probably done the same thing, seeing as it was the only piece of evidence that would get his accuser to shut up.

Of course she looks young...porn producers try to find young-looking people to take naked pictures of. Type "barely legal" into any search engine. All you've proven is that you can sway 1/3 of people into believing that a fuzzy picture of a youngish naked woman is child porn without any other evidence.