Philip Gluyas, 49, an umpire in the Ballarat junior football league with Asperger's syndrome, claims to be living in fear after anti-autism blogger Oliver Canby urged people to kill him in a series of posts on the website 'Autism is Bad'.
Canby, who lives in Los Angeles, wanted people to show up at Mr Gluyas' Sebastopol home and murder him, the Supreme Court was told on Tuesday.
Canby, who does not believe Asperger's exists, claimed he would offer a $500 reward to anyone who carried out the murder.
Mr Gluyas, an outspoken advocate for the rights of people with autism, is suing Canby in the Victorian Supreme Court for defamation claiming he had made false and malicious statements about him, exposing him to hate, ridicule and contempt.
Mr Gluyas, who runs the blog 'Phil Gluyas: Autism News and Views. The truth about Autism is here', was first diagnosed with Asperger's in 1997. The condition is considered to be part of the autism spectrum.
In his statement of claim, Mr Gluyas revealed one of Canby's posts on the 'Autism is Bad' website went on to say: "Just to clarify, this is a threat of bodily harm, as well as a threat on Phil Gluyas' life".
Canby also wrote: "I hope someone comes to your house with a knife tonight and saws your head off".
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.