Most acts of jackassery are the blend of ignorance (or worse, obliviousness) with confidence (or worse, over confidence). Let’s put it this way, there are very few humble and thoughtful jackasses.
A litmus test might be the emotion of regret, as in “I can’t believe I was such a jackass!” The presence of this emotion increases the likelihood that there was a moment of jackassery. But then again, most jackasses aren’t prone to reflection.
At the end of the day, we have to rely on that old saw, “I know it when I see it!”
Please note we just can’t keep up with the inventiveness of a good jackass. Jackassery is, after all, a bit of genius.
That’s what makes it so interesting.