52% sounds impressive, but how many percent of total UK interactions with the site is that? Probably in the range of 0.01%, to be generous.

We're giving away our freedom for 0.01%. "But think of the children!"

If you're using Facebook services, you gave your freedom away a long time before this.

They could be technically correct. Most crimes follow a pyramid of sorts with lesser level offenses on the bottom and the impressive stuff at the top (e.g. there are many drug dealers but very few kingpins). They probably have some sort of low level "soliciting a minor" type of crime to criminalize grooming and of course most of that is going to happen over whatever the dominant communication mediums are, Facebook in this case