An upset initially looked to be on the cards when Knights prop Kade Snowden crashed over untouched in just the 2nd minute.
But it took only three minutes for their dream start to turn into a nightmare, as Rabbitohs centre Dylan Walker finished off a 60-metre blindside play that also saw opposite three-quarter James McManus's night end with concussion.
The early setback seemed to flick the switch for the defending premiers, with Johnston burning Chanel Mata'utia in the 10th, John Sutton offloading for Inglis in the 15th and then Bryson Goodwin going over on play one of a scrum win in the 23rd.
Co-owner Russell Crowe was watching on from the stands and the only opponent the Rabbitohs seemed to be playing was the clock.
The carnage continued when Inglis stretched out to nab his second try in the 27th. Walker notched his brace in the 33rd, before Inglis celebrated his hat-trick in the 40th by bringing out his goanna celebration.
By the end of a first half, the Rabbitohs led 36-6.
The points somewhat dried in the second half, with Thomas Burgess crashing through in the 49th, Johnston soaring over Mata'utia in the 59th and then Walker effecting his own hat-trick in the 73rd.
A shellshocked Knights coach Rick Stone apologised to the club's fans for his squad's porous effort.
"I'm embarrassed to be honest. It's probably a fair time to apologise to our fans, particularly for the first half," he said.
Newcastle captain Kurt Gidley echoed his coach's sentiments by saying it was difficult to thank their travelling supporters for turning up.
"It was embarrassing. It's hard to look them in the eye, thank them for the support and turning up to the game when we play like that in the first half," he said.
"It's as bad as it's been. I'm physically and mentally exhausted after that."
Rabbitohs coach Michael Maguire said the dominant performance was a result of having his entire squad at full strength - only back-up rake Cameron McInnes is sidelined - and on the training paddock.
"To be able to play like that, with the combinations of the boys are gaining momentum with, is what we're looking for," he said.
"We've got the combinations that are being able to be settled at training now.
"We've obviously gone through a period throughout the season with the spine being disjointed at times.
"But we've been able to now really look at our game and focus on the things that we hold high in what we do."
- AAP
