I have to say that I don't talk about credentials because they really are an inappropriate source of authority on the internet.

I instead link to authoritative references.

It seems like you're missing the distinction being drawn between high blood sugar (but adequate levels of insulin to prevent ketosis) and very very lowlevels of insulin. The former is bad over longer time scales; the latter can become ketosis/acidosis/an emergency quickly.

But neither that, nor is whether he should offer credentials the point. The point is you said this:

> > > Sorry to be crass, but this type of argument is exactly why non-experts shouldn't be talking about topics they aren't experts on.

I think there's a little recalibration necessary if the person you said this to turns out to be pretty well educated and capable in the subject.