Supreme Court Justice Jack Forrest said on Tuesday that disabled pensioner Philip Gluyas sued Los Angeles resident Oliver Canby for defamation over a series of internet blogs between 2011 and 2012.

Justice Forrest said he was satisfied Mr Gluyas had been seriously defamed by Canby who falsely claimed Mr Gluyas did not have Asperger's and was a paedophile, homosexual and sexual deviant.

In one post titled "A call for violence against Phil Gluyas" on Canby's website "Autism is bad", Canby offered $500 for someone to murder Mr Gluyas at his Sebastopol home.

"I don't just want him to die I want him to suffer it has to be done right," Canby said in his post. "After you are done decapitating him, please mount his head on a stick and roast it over an open fire. The rest of him can be dismembered and tossed into the ocean."

Canby, who believes Asperger's does not exist, said he would need proof before sending the killer $500.

"If any perpetrator is charged with a crime as a result of this, I will fully pay for your legal defence and present this to the courts as justifiable homicide."

Justice Forrest said while it was evident only a small number of people would have read Canby's posts, he was conscious of a possible grapevine effect "particularly given that some of the defamatory material may still be accessed by a web search".

"I consider that that defamatory imputations are serious and that Mr Gluyas is entitled to an award of damages that vindicates his reputation and standing."

The judge said it was appropriate to award Mr Gluyas, who had been represented by Chris Twidale from the Victorian Bar duty barristers' scheme, an amount of $50,000 in damages plus $6900 in interest.

Outside court, Mr Gluyas told Fairfax Media he was delighted with the decision, but he continued to be in fear for his life.

Mr Gluyas, 49, an outspoken advocate for the rights of people with autism, runs the blog 'Phil Gluyas: Autism News and Views. The truth about Autism is here' and was first diagnosed with Asperger's in 1997.

The condition is considered to be part of the autism spectrum.

Mr Gluyas was previously awarded $54,000 in damages in a separate defamation case in 2013 against another US anti-autism blogger, John Best, who lived in New Hampshire.

Best had claimed all forms of autism were caused by mercury poisoning and could be cured by a form of treatment known as chelation. But Mr Gluyas challenged this view, posting how conditions on the autism spectrum were congenital and could not be cured.

In one of Best's posts on the "hatingautism" website, he claimed an AFL official should be informed of "the deranged nature of the psychopath Gluyas", claiming Mr Gluyas suffered from a serious mental disorder that caused him to be violent towards others.

Best even compared Mr Gluyas to the serial killer Hannibal Lecter.

Mr Gluyas rejected the claims and successfully sued Best for defamation.