Very well said, but
even if we were talking about just CSA, this is
still bullshit: the one thing you can do to help prevent child sexual abuse is to talk to children about sex, taboo-free, and have quality sex ed starting at primary school children. Emphasising consent, explaining what is sex and how it works, how it's not okay for an adult to do it with you, how it's not okay for anyone to touch you without your express consent, inculcating healthy views about relationships and sex from an early age, etc.
Unfortunately this is uncomfortable for some people (understandable, it's pretty awkward to talk with a 7yo about sex), but it's what politicians should be pushing if they were really about "saving the children". Monitoring cell phones is not it.