In the video, Amie Carter's son Jayden, who was two at the time it was filmed, was refusing to get in the car because he was upset a game had gone wrong.
Jayden was screaming and crying while his mum had to try and pull him into the car.
Shortly after this video was filmed, Carter learned her son had autism.
Without knowing the circumstances, an internet user, Mike Steele, shared the video on his own Facebook page with the phrase: "Spare the rod, spoil the child", referring to when a parent doesn't discipline their kids.
After learning the circumstances, Steele updated his post.
"Just by observing this mother with her son it appears that it’s a little boy misbehaving and the mother is being patient with her son," he wrote.
"Little did I know, this little boy name is Jayden; he is diagnosed with autism.
"I didn't know until his mother contacted me. It’s funny how we can see a video and add our twist to it.
"Now that we know this piece of info, how would you really react to your child whose diagnosed with autism?
"We probably would have reacted the same way she did… Let this be a lesson to us all and let’s join hands to understand autism as a whole.
"Sorry Amie and Jayden."
Steele's video post has been viewed more than five million times since being uploaded 19 June.
Since updating his Facebook post, there have 34,000 comments with many people praising and defending the mum.
"As soon as I started watching this (before reading the description), I wondered if this little boy has autism," one person commented.
"Autism meltdowns are no fun. But honestly I believe that autism or not, this mother did what was appropriate at the time.
"And for people saying that physical discipline would be better, in this situation, it would almost certainly make things 100x worse."
Another person wrote: "It makes me sad and very upset with the judgmental and ignorant adults who assume things before knowing all the facts!
"I have a son who is four and has development delays and I get all the looks cause he looks normal but his speech is not their and he has tantrums I can't control in public."
Carter originally uploaded the video six years ago and uploaded it to YouTube.
"I originally posted a video back in 2010 of Jayden having a 'tantrum', it was before he had any diagnoses," she wrote.
"It was the first time I couldn't get him in his car seat... I smiled, and SMILED... due to the fact we had an audience watching us (it started out inside the restaurant) and I was embarrassed."
The mother told Scary Mommy: "I honestly chose to post it because I was mad and frustrated with the system and its lack of support. I was mad because I had been speaking out, trying to get help.
"I decided to be a voice and posted the video."