This is commonly referred to as Men-Who-Know-Things Syndrome. And, it's aptly described here:
"...[T]he out-and-out confrontational confidence of the totally ignorant is, in my experience, gendered.
Men explain things to me, and to other women, whether or not they know what they're talking about. Some men. Every woman knows what I mean. It's the presumption that makes it hard, at times, for any woman in any field; that keeps women from speaking up and from being heard when they dare; that crushes young women into silence by indicating, the way harassment on the street does, that this is not their world. It trains us in self-doubt and self-limitation just as it exercises men's unsupported overconfidence.
....[E]xplaining men still assume that I am, in some sort of obscene impregnation metaphor, an empty vessel to be filled with their wisdom and knowledge."
I have had these moments. Related to the world wide webs, a couple of times I have had the bizarre experience of having a group of virulently anti-gay blogger doods inform me that I just needed them to walk me through my "misconceptions about marriage and family" and then I would understand the errors of my thinking. Even though these men are barely literate, possessive of marginal reasoning skills, and lack a degree in any subject relevant to the marriage debate, they essentially instructed me to shut up and take notes on what they were saying.
I've seen this over and over again on the world wide web. In addition to the "commonsensical" rantings of self-anointed political pundit doods throughout the blogosphere, we also see this unsupported overconfidence rear its ignorant head in folksy folks like Joe the Plumber. In this white conservative anti-gay guy we see the arrogance of those who claim to be a "metaphor" for Real Americana, as though there is any such thing as a default American. In Joe, we see how White-Dood-as-Default Syndrome often works hand in hand with Men-Who-Know-Things Syndrome to produce mass delusions of grandeur.
I think the phenomenon can best be expressed in a mathematical equation:
Unearned Authority of the Male Voice + Man's Status as Default Human Being = Unsupported Male Overconfidence.