Stanley Bruce Early, 77, was convicted of murder by a jury in June for the fatal Sydney bashing of the 43-year-old married man, who he perceived to be gay.
The attack happened at Randwick's Alison Park on a night in 1987.
On Friday, a person - who cannot be identified for legal reasons - had a statement read in court, accusing Early of only feeling sorry for himself and failing to acknowledge his actions.
"Early is a troubled person who not only murdered (Mr Keam) and got away with it for many years but he also destroyed the lives of many other gay men for no reason," Early's NSW Supreme Court sentence hearing was told.
"The soulless monster that murdered him was still out there living his life while (Mr Keam) was buried in the ground.
"Because of you and your desire to 'clean up' Alison Park, you stripped the world of a loving father, partner, friend and mentor."
The person hoped Early would live the rest of his life "miserable and broken" in a jail cell thinking about what he had done.
"Will you feel remorse one day? I don't know and to be honest I don't care anymore," their statement said.
"I choose not to forgive you but to forget you and never think of you again as it's what you deserve."
During the hearing, Justice Dina Yehia indicated she would find that Early attacked Mr Keam due to a hatred or prejudice against homosexuals and this was an aggravating factor in her sentencing.
Public defender Troy Anderson SC said Early targeted his intended victim through a desire to inflict grievous bodily harm but did not intend to kill.
He said it was unclear whether Early himself or others in his criminal group delivered the fatal blow.
Evidence during the trial showed Early was the ringleader of a gang who beat up men they perceived to be homosexual at Alison Park, which was known as a gay beat.
"It seems that the modus operandi of this gang was to obviously assault their victims but this is an instance where it went beyond what normally occurred," Mr Anderson said on Friday.
Judge Yehia heard that Early had no criminal history after 1991 and that he would be sentenced based on jail terms handed down at the time of the hate crime.
"The sentences that were imposed for murder in the late '80s and early '90s were lower than the sentencing practices currently," she said.
The 77-year-old is housed in Long Bay Prison and had been admitted to the psychiatric ward for three to four months while there, the court was told.
Mr Anderson said his client recognised that he was likely to die in jail due to his age.
Early had been diagnosed with depression and was the victim of sexual assault himself earlier in life, his barrister said.
"He's a person who's had some difficulty with his family over the years and seems to have lived a fairly isolated and sad life."
Crown prosecutor Ken McKay SC rejected defence submissions that Early would have good prospects of rehabilitation, saying the court should be "guarded" about this.
Justice Yehia will hand down sentence on October 20.
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