All right.
I see that mostly not explicitly illegal material is posted and yeah some arguments can be raised to move the goalpost.
Such argument can be the legal age, but sometimes this is misunderstood, for example on the Hungary one can have consensual sex with a 14+ grill but pornographic material (photos, videos etc.) can only be made and owned if the grill is 18+ so for example if a dude keeps nudes of his 17 yo. gf even that counts as illegal. Just checked the law for Hungarians who are interested: Btk (2012. évi C. törvény) 204. § which defines what can be pornographic material but it gives a wriggle room which can be used to dispute what counts as such. For the intention of owning certain pictures: the posters you mentioned post non-nude child models I check the thread the pictures gets downloaded by the browser, then the authorities can examine what I do with such pictures. Am I a talent scout who looks for young models for fashion business or whatever? No. Then what am I doing with such pictures even if they aren't sexually explicit materials? This calls for trouble. But even if Bernd/Anon don't get legal punishment, it can further destroy his personal relations. There are always people who will look contempt on Bernd after such thing come to their knowledge, this "oh but I don't even step outside for years now" or "oh I'm such a recluse" argument is a BS.
Keeping "the normies" away is also a shitty argument, then why not just post gore 24/7? And most of the Bernds browse reddit and such places anyway. Also who the fuck wants to come to any KC related boards from the normieweb?
Nevertheless those type of threads aren't /int/ related and even if not outright bannable offenses it isn't a reasonable idea to move/direct them to a board exclusively maintained for those or fit more into the theme like /b/. I think you did good to suggest such solution.
Here not long ago the Russian authorities asked the removal of some lolicon images from /librejp/. We were against the deletion you still can find discussions in some threads, and while it fits to /librejp/ I don't really want such posts here. But here on /kc/ it can be easily ignored if it is posted on an occasion, and if it gets repeated it can get deleted as spam. And again the intention, now I wrote this maybe someone gets the grand idea to test what I wrote in practice but then it is obvious why is that posted and I can report that content.
Personally I think we shouldn't tolerate such content for the reason Brazil Bernd wrote: it's a slippery slope, we don't need such people here. An occasional discussion on age of consent and such (like the one that gifted a banner) is fine and fun but dumping hundreds of little girl/boy pictures isn't belong here.
I'm for freedom of speech and opinion but this isn't even fall into either category.