I'm all against protecting morality and leaving it up to people's responsibility and free will. But kids don't have free will. They'll mostly agree with the nearest source of authority and believe it with all their heart.
Parents should filter, of course, but every time they block content, they get the bad-guy sticker. Why make it happen more than necessary. Plus, uninterested parents make terrible judge of what is harmless and what is too much. Search your memory.
It's true that it's hard to draw the line. Pokemon is a good example (as well as Transformers and He-man, for the older crowd :) ). But in those cases, what was sold was what was on screen (in a much idealized version): action figures.
But, Ok, the line is hard to draw. Now I still think it's better badly drawn than not at all.