Yes I have. Those over creative cartoons that require extensive concentration such as Horton Hears a Who, I find that hard to understand at first. Hence, the children especially non English speakers would find it hard to understand too.
Some anime's aren't really appropriate for young children but most children's cartoons are given the tick of approval from a board. If parents etc feel strongly that it's not appropriate they can put in their reasons and it will be evaluated and if found to be then it will be removed or be asked to make changes to be more suitable.