You can't blame children for the environment they're born into. You can only blame their parents' and grandparents' (and so on) generations for that. For example, the ones who grew up with returnable pops bottles, but decided as adults that it would be better to buy "disposable" plastic ones instead. There are plenty of adults that say this, but they come with a sense of complicity because they were part of the generations that created the problem. When a child points it out, it's more powerful.