Why am I being punished?!

Dear Rabbi,
Why does diabetes exist in spite of the fact that (1) no one sins before he/she is born to deserve being created with diabetes or any other hereditary disease, all other diseases, disabilities, defects, or bad genes in the first place and (2) it is not fair that G-d punishes people for the sins that their ancestors committed instead of only punishing the sinner like, for example, the reason why a diabetic is a diabetic is because 10,000 years ago, his/her ancestor was a bank robber and G-d punished that bank robber by decreeing that as punishment, his/her descendants will have a disease called diabetes? I am therefore very angry at G-d and I demand that diabetes, all other hereditary diseases, all other diseases, disabilities, defects, and bad genes be eliminated immediately! Please answer all my questions and please reply.