When Robb Scott overheard another father telling his son last weekend that Down syndrome was an "illness of not knowing anything," he said nothing.

But as the father of a five-year-old boy with Down syndrome, he felt sick inside. Sitting in his car afterward, the Truro, N.S., dad poured his heart out in a video, one that has now reached more than half a million people.

Scott had been picking out a movie when he noticed the man's son select Where Hope Grows, a film about a man with Down syndrome. That's when the boy asked his dad: "What is Down syndrome?"

Turner Scott's father says: 'It's not an illness. It's not even a disability.' (Courtesy Robb Scott)

"I didn't think his dad was trying to be mean," Scott says in his video. "I could see he was searching for the right thing to say, and he said it was an illness. And that it was an illness of not knowing anything. It's one of those moments where you don't know how to act, you don't know how to react. I didn't say anything."

Fighting back tears, he continues: "I let that ignorance grow in another generation and failed my son. I don't mean to get emotional about this and be an exhibitionist about this, but I have to reset that button, because I failed him in that moment.

"Down syndrome is literally the most beautiful thing that's ever happened in my life. It's fun, it's brilliant, it's amazing, it's funny, it's kind, it's loving, it's cuddly. They're great teachers, people with Down syndrome. It's not an illness. It's not even a disability."

After gathering himself, Scott continues talking about how his son Turner has changed his life.

"Just because you read slower or don't run as fast, does not mean you have a disability to me. This is what I learned from Turner. Disabilities are perception," he says.

"Down syndrome is the best thing that ever happened to me, but I didn't say that. I didn't step up for my son and for other people with Down syndrome. And that was devastating to me in that moment. So I just wanted to right that publicly for myself."

Blown away

Scott told CBC News that as of Tuesday morning, the Facebook video has been viewed more than 500,000 times, shared 7,735 times, and has drawn more than 2,000 comments — many from other parents of kids who have Down syndrome.

Scott and his wife, Kelly MacIntosh-Scott, live in Greenfield, just outside of Truro, with Turner and seven-year-old Griffin. Scott creates sports art, and his work videos don't usually gain that sort of traction.

"It's just blown me away. It's certainly made up for it. To think that I missed that opportunity with those two kids, but now what it's doing? There's something karmic about that."

Scott says that before he and his wife had Turner, they knew nothing about the condition.

"I'm not judgmental that way," he says. "I understand, because I didn't have a clue what Down syndrome was before my son was born. I looked at it the same way and I probably would have said the same thing."

Turner needed a lot of medical care in his first few months and Scott praises the hospital staff who helped him.

Taught him plenty

"When they said, 'Your son has Down syndrome,' it was terrifying to me, because I had no idea," he says. "But the information they give you is all bad, it's all scary. 'Here are the things that can go wrong.'

"Nobody comes in and says, 'Hold on — congratulations! This is a spectacular thing. Here's what you're going to learn, here's what you're going to do.'"

He says he cried every night for a week, because he was so worried. But Turner has taught him plenty in the five years since.

"If you want my son to teach you how to be the CEO of a business, it's not going to happen," Scott says. "He's not going to be a world-class runner. But if lessons of love and caring and acceptance and honesty are important to you, there is no better teacher. He had taught me so much."

He's also taught him some fly dance moves.

And everyone do the Wop!!! Or whatever the heck dance my son is doing. <a href="https://t.co/q0zzmH8K7O">pic.twitter.com/q0zzmH8K7O</a> —@RobbScottArt

Turner has also encouraged his dad to rethink success.

"You begin to explore the other gifts that he has. Once you realize them — he's incredible. I don't know anyone he's been around who doesn't want to hug him and squeeze him and love him. He just makes you feel happy and feel good about yourself. That's his gift."

But to other parents learning their child has Down syndrome, he does have one warning.

"He's just as much a pain in the ass sometimes. When he's too slow getting ready for school, you get upset with him. You love him and you hug him in the happy moments. My wife and I, our relationship with him and our oldest son is exactly the same. It's the same problems, the same great things. Nothing is different."