I like the content provided in this article because it brings to light some of the pitfalls associated with absolute propositions. Web content filtering is a valuable and practical tool. So is network layer scanning. But the application of these practices is not an absolute solution to a security problem. These are steps or layers in a security methodology. There are no absolutes when it comes to cyber security assuming you are going to plug in or turn on a computer.
Risk levels can be lowered through sound practices, but risk can never be eliminated. The world of IT and cyber security is simply too dynamic.