Ignorance is high and a publication like PCWorld isn't going to draw the most technically knowledgeable individuals. Combined you end up with comments like the one you quoted where the poster is completely ignorant of Linux market share (6% overall I believe for real computers and it has a virtual monopoly on things like home routers).
Most people are deluded to believe that they are completely normal so if you aren't exactly like them and using exactly the same tools that you are somehow a highly unusual freak. This type of thinking is very common in humans and a big aspect of psychology. Such beliefs are heavily exaggerated in some mental diseases like schizophrenia where they believe they are the most important person in the world and anyone that doesn't believe like they do is dangerous or insignificant.