Every time I hear it, it is offensive. Let me explain why.
It's often quoted in the context of a relatively young person who has died and people discussing the young and sudden death as 'well, they were diabetic, so they died because they just kept eating donuts and didn't stop when they were told'. That brings no comfort to the family and it is often completely untrue. Most diabetics do try very hard to deal with their condition responsibly but simply stopping eating carbohydrate is not really a 'cure' or answer to the condition. Some may chose to deal with it, in part, by doing this because they feel that helps them specifically. But that is not the case for everyone.
Anyone who said a cancer patient died because they brought it upon themselves would rightfully expect to be ostracized (or worse) but, for some bizarre reason, people are happy to unquestioningly accept the point for diabetes, but not cancer (another disease with complex reasons behind it).
Addressing some other comments, insulin resistance can be a natural condition due to genetic factors and occur in the absence of excessive carbohydrate consumption. It can also develop in type 1 diabetes as a reaction to the artificial insulin introduced to control the condition (GM 'human' insulins can help but sometimes switching to Bovine/Pork insulins helps - again, it's complex and not well understood). Low carbohydrate consumption may mask the condition, but the person is still insulin resistant/diabetic regardless of whether they eat carbohydrate or not. Diabetes is not cure-able (yet - there are pioneering attempts).
I know diabetics devastated with guilt that they've somehow caused their diabetes and are responsible because someone told them it is because - based on no evidence at all - they eat too much sugar.
Perpetrating this myth and forcing guilt upon diabetics is potentially psychologically damaging, especially to a group know to have a higher propensity to depression because of the condition.
My final point on the matter, some diabetics have a form which is virtually impossible to manage manually and the only avenue for treatment is to use the new insulin pump technology which can combine continuous glucose monitoring with ultra-fine insulin control (complex time slot/insulin sensitivity/carbohydrate dosage calculations) in order to control the condition. This is showing excellent results but does come with considerable costs - although these are a small fraction of the cost of amputations, blindness or organ failure which can otherwise result.