Magistrate Suzette Coates admitted the pair was effectively saved from heavier punishment after being targeted by hacktivist group Anonymous, which had published their personal details online, prompting vile abuse.
“Those cyber space warriors … (acted) in the same category in which you acted – nasty, vicious,” she said.
But that didn’t wash with outraged RSPCA chief executive Mark Townsend, claiming Ms Coates was out of step.
“They will be going home to sleep in their comfortable beds, no fine, no community service,” he said.
“They’ve basically walked away without any consequences for their actions.
“The possum crawled away to die a lingering death while the perpetrators laughed and posted their heroic deed on social media.
“Forget about being vilified. They were the ones who put it out there in the first place.”
The court heard Jonasen ran over the possum on Christmas Day last year, causing its eyes to bulge, its spine to snap and its entrails to hang out as it tried to flee into bushland without the use of its back legs.
McKenzie posted the gruesome act to Snapchat, where someone who viewed it recorded in on their phone and reported it to the RSPCA.
Prosecutor Greg McGuire said not only did the pair commit the act, record it and then disseminate the recording but, most disturbingly, they “found it amusing”.
However, he didn’t seek jail sentences for the teens given their age.
“If these were mature-aged men, in my submission the court would have no alternative than to impose a custodial sentence, with an actual custodial requirement,” Mr McGuire said.
Ms Coates said it was their “good luck” that Anonymous had targeted them, and she also took into account the fact the pair had made wooden “possum shelters” to give to wildlife groups after being charged.
RSPCA senior inspector Georgia Sakrzewski said she was disappointed by the punishment.
“It’s pretty easy to go out and knock up a few wooden boxes and say you’re sorry,” she said.
Jonasen and Mckenzie were also ordered to pay $339.80 each in costs.