Blocking the display of images client side that contain large amounts of uncovered flesh isn't going to do shit to prevent the accidental access of child pornography.
And seriously, how often does that actually happen? This is just another 'think of the children' argument designed to disable critical thinking.
It's not a 'think of the children' argument, it's a 'generally avoid suspicion for crimes with awful punishment' argument. Same as how if there was a known hitman's forum, I'd block access to that too.
Your cite is flawed. Or at least the conclusion you draw from it. The only conclusion that can be drawn is there is a greater number of infected non-smut websites than smut websites. This says nothing about the frequency of infections of smut websites vs. non-smut websites- in other words, it says nothing about the odds of infection given the fact that you are visiting a smut or non-smut website.
And seriously, how often does that actually happen? This is just another 'think of the children' argument designed to disable critical thinking.
And as for your first (uncited) assertion, consider the following: http://www.theregister.co.uk/2010/06/30/unsafe_surfing/ Summarized: regular websites host more malware than sites dedicated to pornography.