It may have been more obvious to a UK audience because we've just had all that Jamie Bulger stuff in the news and this had some parallels, plus we are generally OBSESSED with paedophilia in the UK and know so many cases of mistaken attacks on paedophiles.
Personally, I didn't try to work it out. I don't feel Wallander is plot or solution driven, it's about character, time and place for me and I concentrate on that.