To make the analogy more fair, let's say your house (filled with people's personal information) had an unlocked secret entrance way, even though many lock experts say that unlocked entrance ways are generally unsafe. People may or may not be going into your house everyday while you're gone, and using that personal information while everyone remains blissfully unaware. One day, someone comes in and takes all the personal information and publishes it to show how insecure it is.
Yes, the person breaking in may be a jerk, but maybe people will put locks on their doors now.
This seems like pretty terrible science. Correlation does not imply causality.
All that they did was observe that people who happen to drink diet sodas also happen to have a (slightly: 2.11cm vs .78 cm) higher increase in waistline. They didn't control for caloric intake, it wasn't doubly-blind, the choice of amount of diet soda consumption was self-selected.
This would be analagous to finding that people who are on diets are fatter than people who are not, and writing a headline saying "Dieting makes you fat."