I blame the media for a lot of the misunderstanding that is rife among people today. Every few days you get a new article telling you that sugar/fat/alcohol/whatever causes diabetes without specifying the type or what exactly happens within the body, so everyone just thinks that everyone with diabetes is obese and can cut down their sugar and fix it. This may be true for a few people but certainly isn't representative of every diabetic of either type!
My worst was at work; was having a hypo and went all shaky, my manager sat me down and I explained that I was diabetic and needed some sugar. She had some chocolate which she quickly gave to me, only to have a colleague say 'but you shouldn't be eating that', despite me having explained the situation! Much as I blame the media for a lot of this, I think some people could listen a bit more as well; it does get frustrating.