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.