These days I often see the word "boomerang" used in an unusual sense. It is used when making fun of disputes. When you have your criticism at your disputant "boomeranged against you," it means that the criticism is also true of you.
It appears almost always the case that when someone correctly points out that your criticism can be true of you, you, a victim of the boomerang, are no longer regarded as competitive.
This consequence of boomerang felt strange to me. But I didn't know why. All I could say was that in face of the boomerang the disputant can nevertheless have their say. Boomerang is no proof of their incompetence or the frailty of their argument.
The other day, I happened to watch this video:CRITICAL THINKING - Fallacies: Ad Hominem [HD] - YouTube
This video taught me that boomerang is a kind of ad hominem fallacy. It made clear the strange feeling I had had about the boomerang argument. Another instance of philosophy telling you how to debate in a meaningful and constructive way.