This is true for a very narrow definition of debate though. At work, choosing to debate can make the difference between a software design that solves the problem vs one that doesn't. Deploying code that causes an incident vs lands safely.

In broader life, public debate can reveal new arguments to seeking minds, help influence and educate people other than the debaters. It can even grow the debaters themselves if they approach with the right humility.

That said, many do approach debate in the way you describe. For those of us trying to avoid futile debate in favor of productive debate, the best choice is to detect these bad faith actors, acknowledge the bad faith publicly, and pull away