There are some more constructive reasons for arguing with the incorrigible. One is to persuade the audience, rather than your interlocutor—anything you say on a public stage is addressed as much to the general readership as to the individual being explicitly addressed. Another is to practise your skill at arguing the material.
Not that these justify going on and on indefinitely, but they are worth putting in the balance.
There are some more constructive reasons for arguing with the incorrigible. One is to persuade the audience, rather than your interlocutor—anything you say on a public stage is addressed as much to the general readership as to the individual being explicitly addressed. Another is to practise your skill at arguing the material.
Not that these justify going on and on indefinitely, but they are worth putting in the balance.