A man had made a hit list of men he planned to kill in his bid to rid the world of paedophiles, a court heard.
Christopher Hunnisett, 28, delivered five severe blows to Peter Bick's head with a hammer before walking into Hastings police station and telling officers he had killed someone.
Hunnisett, of Chanctonbury Drive, Hastings, denies murdering 57-year-old Mr Bick at his flat in Bexhill on January 11 last year.
Philip Katz QC told the court there was no evidence that Mr Bick, who was gay and enjoyed consensual sex with young men, was a paedophile, or that any of the men Hunnisett had contacted through the internet and added to his hit list had ever wanted or had relationships with children.
He added that during his plea and case management hearing in October last year, the jury was told Hunnisett said: "It is not wrong to try and stand up to evil in this world. Not guilty," as the murder charge was put to him.
Lewes Crown Court was told this was the third time the defendant had been tried for murder.
In 2002, Hunnisett was convicted of killing the Rev Ronald Glazebrook at his home in St Leonards on Sea, Mr Katz said.
During the first trial, the defendant maintained that he had found the vicar dead, having drowned in the bath, and he had enlisted a friend to help him dismember the 81-year-old's body and get rid of it.
In the two weeks Mr Glazebrook was missing, Hunnisett, who had met the vicar through the church as a young boy and was the man's lodger, "repeatedly and successfully lied" to the vicar's daughter, family, friends and police that he was unaware of Mr Glazebrook's whereabouts.
Mr Katz said: "When his body was discovered and when Christopher Hunnisett was arrested and interviewed under caution, he gave a bizarre story about aliens being involved."
Following his conviction, material came to light which discredited Mr Glazebrook's character and showed he had sexually assaulted a young boy, the court was told.
Despite Hunnisett maintaining throughout the first trial that his relationship with Mr Glazebrook was purely platonic, he went on to tell a prison chaplain and doctors that he had been sexually assaulted by Mr Glazebrook, the barrister said.
Over the years the level and frequency of abuse increased, with the defendant alleging to many different psychiatrists there had been regular serious sexual abuse, he added.
The court was told Hunnisett successfully appealed against his conviction and was retried for Mr Glazebrook's murder in 2010.
He was acquitted of the vicar's murder on September 18, 2010, and went home to live with his family in Hastings, the court was told.
But less than four months after his release from prison, Hunnisett walked into the police station and said he had killed someone, Mr Katz said.
He said there was "not a shred of evidence" that Mr Bick was a paedophile but what he did enjoy was consensual sex with young men, including the defendant.
The jury was told they would hear evidence from a young woman who had a relationship with Hunnisett following his release who would tell them about his "varied and colourful sexual preferences" and his plan to kill paedophiles.
Mr Katz said: "Suggestions were that he had planned to kill more men who he had been in contact with over the internet. He had a hit list and Peter Bick was top of that list."
He said the defendant's claim that he was on a mission to protect the world from sexual offenders was the "false claim of a cold-blooded killer".
He said Hunnisett had admitted killing Mr Bick and did not dispute that he intended to do him very serious harm, but his mental health at the time of the incident was being called into question by the defence.
He added: "We say this was brutal, carefully planned murder for which this defendant is seeking to escape responsibility in any way he can."