One big issue is how hard it is for anyone to change their ways (or in this context, their treatment for diabetes) once it has started and once the "routine" is under way. Some of us are creatures of habit, especially if the habit is prescribed by a doctor or nurse.
We've got people here who were on the "conventional" treatment for a long time, sometimes years, before making diet/lifestyle changes after finding this forum or another source of alternative advice. If anything, changing course months or years later requires a lot more courage than just adopting it at diagnosis.
To me that's an argument for being (politely but firmly) fairly insistent, even with a scared and confused newbie. I'm not advocating for ramming stuff down people's throats (and I seldom see that happening here), but I do think getting the message out quickly is unlikely to do harm and quite likely to do some good.