The ground for taking ignorance to be restrictive of freedom is that it causes people to make choices which they would not have made if they had seen what the realization of their choices involved.
If one takes full account of the persecution of heretics, the frequency and savagery of the religious wars which Christianity had endangered, the harm caused, especially to children, by the pernicious doctrine of original sin, a case could be made for saying that the world would have been better off without Christianity.