Is it permissible to delete pornographic films from customers' devices, given that the saying "Whoever among you sees an evil, let him change it with his hand" applies to those in authority?

Whoever is able to change an evil with his hand must do so. It is not a condition that he be a person of authority or that he be granted permission. Rather, the criterion is the ability and the balancing of benefits and harms. So, if deleting pornographic films does not result in greater harms, then it is a prohibition of evil and he will be rewarded for it. Otherwise, he should move on to denouncing it with his tongue.