It might help to substitute "ignorance" instead of "innocence" in your essay. To be innocent primarily means to 'do no harm' not "to be ignorant" of the truth.
I think many parents keep their kids ignorant (of evil) because they think it will help keep them innocent (free of the sin of committing evil). As you imply, for a time, this seems right, but eventually you need controlled exposure to toxins (ethical, etc.) to learn how to protect your self.