This is a phenomenon I encounter here and at other message boards. The topic doesn’t matter, it is the tone I am trying to capture in a word or phrase. It is where the writer makes a statement that is just their opinion but they make it sound like established fact.
The writer may be guilty of a logical fallacy of one kind or another, or maybe they should have used cites, but that’s not what I’m after. I’m looking for a word or phrase to describe the tone of someone who posts like that – authoritative but without the actual authority.
The word that immediately comes to mind is “aver”. However, that doesn’t quite cover it. I think you are looking for a word that describes something that is understood by readers/listeners to be opinion masquerading as fact. My quick google search does not find a single word for this phenomenon.
Those are both accurate when considering the content, but I am interested in the tone, what you might call the tone of voice (in typed content) of such posts.
It’s the sort of term you would be able to use to fill in this sentence: “Your posts are too ________.”
“Overconfident” is about the best single word I can think of and that’s pretty value-neutral. If you really mean you want a pejorative word connoting “You do the over-authoritative thing and it’s bad that you do that.”, I can’t come up with such a term.
“Officious” is a term for behavior sorta like that. Overweening authority, a petty tyrant, especially in a bureacratic manner or context. But your scenario isn’t quite that.
Here is a nice list of common logical fallacies. What you’re describing might be considered Begging the Question (which doesn’t mean what many people think it does).
Begging the Question (also called Petitio Principii , this term is sometimes used interchangeably with Circular Reasoning): If writers assume as evidence for their argument the very conclusion they are attempting to prove, they engage in the fallacy of begging the question. The most common form of this fallacy is when the first claim is initially loaded with the very conclusion one has yet to prove. For instance, suppose a particular student group states, “Useless courses like English 101 should be dropped from the college’s curriculum.” The members of the student group then immediately move on in the argument, illustrating that spending money on a useless course is something nobody wants. Yes, we all agree that spending money on useless courses is a bad thing. However, those students never did prove that English 101 was itself a useless course–they merely “begged the question” and moved on to the next “safe” part of the argument, skipping over the part that’s the real controversy, the heart of the matter, the most important component.