Nobody's saying it's all somebody else's fault.
The only valid position to hold about this topic is that it's complex and multi-faceted.
Sure, self-discipline and personal choices are a factor - but the issue of what influences people's ability to exert self-discipline and make healthy choices is a vast and little-understood topic in its own right.
Whatever the case, if a child is raised on a high-carb/low-fat diet from a young age because their parents and schools accept the official advice, the carb-dependent metabolism they end up with by the time they reach adulthood will most certainly complicate their ability to make healthy choices.
> you still got addicted to it, you allowed it to happen
Societies everywhere restrict access to alcohol and tobacco to minors because it's accepted that minors are not capable of making fully-informed choices.
Why do you hold a different position regarding sugar?