To wonder why can't police do anything when Red rose uk make false allegations on Facebook?

[Loadsalies]

This has happened to 2 people I know. Being branded paedophiles. One historic article posted was doctored and the man in the article looked nothing like my friend's relation. Then his photo was posted in comments. It's causing them horrendous stress. It's someone with an ongoing dispute with them that's instigated this.
The other one had his photos posted and yet more false information. Stuff he'd have been locked up for if it were true.

The police said they can't do anything? Yet people have been arrested for next to nothing before.

"You are a paedo" - defamation, not a criminal offence
"You are a paedo and we are coming to burn your house down with you in it" - threat to kill, a criminal offence
"You are a paedo and someone should burn your house down with you in it. If anyone fancies doing this he lives at 24 Acacia Avenue, get your pitchforks out" - incitement, a criminal offence

I'm guessing that what happened to your friends falls into category 1.

Give that it is potentially incitement I suggest that the Police could do something if they wanted or were pushed

Could it also be harassment?

There's definitely a lot of overlap between online defamation and harassment, which is of course a criminal offence.

This is a good explainer of where the line can be drawn:

"Judges try to look closely at the true nature of the wrongdoing. If the main harm comes from false statements that spread to others, the claim would leans more towards defamation. If the main harm comes from repeated behaviour such as direct messages, repeated online tagging or ongoing attempts to cause fear or humiliation, the claim is likely to lean more towards harassment."

from https://defamationlawyer.co.uk/what-is-the-difference-between-harassment-and-defamation-in-english-courts

Oh there's definitely threats. Need the rope etc and worse.

In that get back on to the Police

Who was the woman imprisoned after Southport well then they might be heading the same way

I told my friend to get back on to the police. I think she has and is seeing a solicitor.