I realise what sort of reaction this will get, so I'll put my hard hat on, but I'm with the Swedish courts on this.
"Mr Grey" is quite clearly an abhorrent individual.
That does not mean that other members of the public can disregard all laws and harass him, or commit any other crime against him, without repercussions. The law doesn't stop applying to you just because the object of your behaviour is a nonce.
We and Sweden have a court system and is not the job of the public to dispense summary justice.
If "Mr Grey" commits a crime then he should be dealt with by the proper legal process.
Vigilantes and paedophile hunters are highly problematic and in many cases actually jeopardise police cases, meaning these people are left to walk the street. She's not a superhero, she's actively making it more difficult for the authorities to prosecute these people.