Both men came off, leaving their bikes to cartwheel at speeds of up to 300 km/h back across the track.
Morbidelli’s machine flew just centimetres past the head of Valentino Rossi leaving the Italian nine-time world champion badly shaken and claiming the stray Yamaha “almost killed” him.
Morbidelli went further.
“Zarco is almost a murderer,” he said.
Zarco won’t take part in Friday’s opening practice for this weekend’s Styrian Grand Prix at the same circuit after undergoing surgery on his injured right wrist in midweek.
His fitness for Saturday qualifying and for Sunday’s race will be assessed on Friday.
Despite his lack of action — and a meeting with the race stewards — Zarco remained defiant Thursday.
“For me it was clear, you have to know that you never try to push someone off the track and I think that on the track nothing will change,” the Ducati rider said, insisting the stewards could not force him to change his approach.
“If they want to punish me, they can’t do anything either. You can’t think like that on a motorcycle.
“If somebody thinks I’m dangerous, it’s not possible to be dangerous on these bikes, you can’t do this sport if you don’t want to take risks.”
Zarco said he was convinced he was innocent in the high-speed drama which also saw his free-wheeling machine also just miss Rossi and come close to taking out Maverick Vinales on the second factory Yamaha machine.
“I explained how I experienced the accident and what I did before passing Morbidelli and after,” he added.
“We have the telemetry to prove what I’m saying.
“They (stewards) asked me questions and then they will wait to see what Franco says. In my opinion, there should be no sanctions because I did not do anything crazy and I hope they understood it.”
Morbidelli, who rides for the Yamaha satellite team, said Thursday he expected Zarco to be punished.
“I don’t think they are going to not penalise him,” said the Italian.
“Clearly Johann took a funny line, a line that nobody has been going on, not even once in the weekend.”
Last weekend’s controversy over-shadowed the second successive win at the Austrian GP by Ducati’s Andrea Dovizioso.
Ducati have won all the races at Spielberg since MotoGP returned to Austria in 2016.
Victory came just a day after it was announced the veteran Dovizioso would leave the team at the end of the season.
World championship leader Fabio Quartararo was down in eighth place last Sunday and his lead in the title race is just 11 points over the Italian.