Relatives of Mr Faulds attended court wearing T-shirts with the victim's photograph and the words "Justice for Billy."
Cousin Peter Wright, 31, said: "They should have got longer. They should have got 25 years. They are animals, cowards."
Evans was at the bonfire gathering in Ruchazie and went to a house with the Harrisons, then returned to the park.
Lord Bonomy said that for reasons not established in court, "you three decided to arm yourselves and disguise yourselves to attack Billy Faulds. Together you took him by surprise and with such overwhelming force (he) was quickly rendered helpless, allowing you to kill him with knives. He was dead within minutes".
Cousin Marie Gallacher, 38, said outside court: "He was left absolutely brutalised."