Cyracuz:
I think that giving more points of view, not less, is always the way to go. If you limit a child to only that which you believe, you are not doing him a service. Only by experiencing many avenues of thought, some good some bad, do we begin to formulate our own opinions about the world. At first, you do listen to your parents as a basis. In fact, studies show that the greatest predictor for political bent and religiosity come from your parents. That seems intuitive to me, although I might argue that on A2K the results would be quite different.
I do agree with you that we should be generally more irreverent to the heroes of the past. We have taken normal people with human problems and turned them into the gods of human thought. They were not gods, just people who had gifts.
This line of yours was excellent:
"Is it possible to teach children the ability of critical thought without telling them what they're supposed to be critical against?" - Cyracuz
My answer is simple: be critical of everything. Let nothing pass unnoticed. That doesn't mean that we should never believe things for our own peace of mind, but always reserve judgement on the things which cannot be proven ("proven" in the scientific sense, not the absolute sense).
Besides, I just don't think it is okay to discount the teachings of philosophers based on their views of (what was current) society. Philosophers, more than anything, teach us how to think and to lay out arguments that normally are indecipherable emotions. In fact, I would say that the most ridiculous philosophers are the most useful, because their fallacies are laid bare for young minds to tear apart, if they are prepared to do so. Our job is to prepare them.