One could also argue this could further _protect_ children. Now, criminal material cannot be viewed by an unintended third party. For example, it is well known that an iCloud hack leaked the photos of many celebrity women and was dubbed "the fappening", only possible because they were stored in a viewable format without e2e.
We should be maximizing the control an individual has over their own data, not minimizing control. Anything the police can easily access is also something tonnes of other people can easily access. Given how common data breaches are, we should simply not trust that the transit/storage process is secure at all.