It seems like this removes one of the best tools law enforcement has available for combatting the production of hundreds of thousands of images of child porn on the dark web.
That being said, much like the similar issue with encryption, I would lean on the principle of least privileges and deny LE this capability until we can _effectively_ make sure it won't be abused. (This applies to facial recognition, not encryption. There's no good enough reason to backdoor all encryption.)
[0] https://www.cnn.com/2018/05/29/us/immigration-refugee-child-...
[1] https://www.reuters.com/article/us-usa-border-trafficking/fe...