The 21st century is the century of excuses. People don’t like being held accountable for their actions and like to blame their problems on anyone but themselves. This is especially true when it comes to their weight and genetics. When you can blame genetics, you’re no longer held accountable for your weight problems and you basically accept defeat.
Person B could have ate green veggies, ditched the junk food and exercised in order to prevent diabetes. Even though person B wasn’t as lucky genetically as person A, they could have controlled their environment and remained disease-free. Despite their poor genetics, they still had control.