While the OP's method is the prevailing one online, there are other means of being an annoying piss-ass. Knowing nothing, but spouting off an opinion anyway is another one that comes to mind. For example, my mom is of the persuasion that all non-Christians of Asian descent both foreign and domestic (whom she refers to collectively as "the Indians") subscribe to a Satan-worshipping religion called "Moslem" and that the founder of "Moslem" was a guy named Buddha. You'll never guess who she voted for. (Hint #2: She also feels that women shouldn't seek the presidency because we're too emotionally unstable for that kind of responsibility.)
I think you can imagine how that kind of stupid irritates many people when spouted off casually as though it were fact. Family get-togethers are always very interesting.