Andrew Young, 40, died after being struck in the unprovoked attack by Lewis Gill, 20, in Bournemouth, Dorset, on November 6 last year.
A chilling video of the assault was released by police.
Andrew's mother spoke of her outrage after Gill was given a four-and-a-half-year jail sentence for the punch that killed her son.
“I saw the CCTV footage in court and you can see that Andrew didn’t cause Lewis Gill any harm," said Pamela Young, 71. "The sentence is an absolute joke."
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Sir Bruce Forsyth, Sir Cliff Richard and the Prime Minister have been among those paying tribute to Cilla Black following news of her death.
TV favourite Cilla Black, who has died aged 72, gave viewers a "lorra, lorra laughs" during her long career.
Some rain in the north. Very warm sunshine in the south