My god, I cannot believe that anyone would feel ashamed or embarrassed about having diabetes! There is absolutely no difference from having a high blood pressure or arthritis, for instance, as it is not something contagious that anyone would need to be concerned about.
And I see injecting insulin in public the same as putting your glasses on to help you see better, as both serve to the same purpose—helping you to survive. You are not endangering anyone by doing one or the other, so please, by all means, do what you need to do whenever and wherever you need to do it, and if some ignorant people try to give you a hard time about it, either ignore them or educate them as it's fine time they've learned their lesson.
And I see injecting insulin in public the same as putting your glasses on to help you see better, as both serve to the same purpose—helping you to survive. You are not endangering anyone by doing one or the other, so please, by all means, do what you need to do whenever and wherever you need to do it, and if some ignorant people try to give you a hard time about it, either ignore them or educate them as it's fine time they've learned their lesson.