I don't really think there's an arguement here. There doesn't seem to be much difference in your respective positions, except, perhaps in your points-of-view.
Permit me, however, to make a small observation. You both are native speakers, judging from your posts, and as far as I can ascertain, you're both speaking English. And gauging from the way you use the language, you're a couple of pretty smart dudes! Yet, I'd also be willing to bet you both are feeling a little misunderstood here. Small wonder then, isn't it, that our students misunderstand us and each other from time to time!
With that, I'd like to support the position John has taken with respect to the separation of responsibilities for language teachers. (My guess is, too, that Roger wouldn't take much issue with this particular point.) The administrators of my school district, and indeed all over California, make the arguement that as long as we're teaching English to our adult students, many of whom come from Mexico or South America as well as from various Asian countries, why not do it while teaching them how to write a check or deposit money in the bank, or address an envelope and mail a letter, and other stuff like that. At first blush, it doesn't sound like too bad a position. But I find that when I try to do that, it greatly interferes with my ability to teach the language. And John is, it seems to me, quite right when he points out that our first responsibility is to teach students English. Even when our adult students have little formal schooling from their native countries, they are adults, and they've either learned how to get by with a lifestyle they're accustomed to, or they will some other way. It is not our duty, as language teachers, to assume that they couldn't manage without our help, and indeed, it seems arrogant of us to assume so. I believe I can be a vastly better English teacher when I don't have to teaching anything but English.
When teaching kids, however, there may be validity to working with them on a broader scale. It doesn't seem much of a stretch to believe you could help them with, as Roger puts it, concepts.
Larry Latham