"He said that is the biggest mistake you will ever make," Simpson tells CNN. "He said there's no way you're going to survive with a name like that. But I just believed in it so much."
Just a few years later, God Is Dope's shirts, hats and sportswear -- featuring "God Is Dope" and "Just God." in white or black letters against bold fabrics -- have caught the attention of entertainers and athletes. The concept is simple: to generate faith-based awareness through fashion, entertainment and influence.
The brand says: "I believe in God in a cool way," says Kayla MaDonna, 27, at the firm's 2,300-square-foot warehouse in downtown Atlanta. "It's a conversation piece that is also aesthetically pleasing."
Faith-based apparel is a rising market with robust competition. But customers say God Is Dope is different because it's an affordable brand that targets young buyers who would otherwise be hesitant to express their spiritually through clothing.
London-based creative director Ant Haynes says it's "the simplicity of it. It doesn't push anything on you. It just says God Is Dope. That's it."
'I need to take this seriously'
Simpson created the brand concept in 2015, when he was 27. He designed a catchy logo, printed it on a shirt and wore it around town.
"If I saw 30 people throughout the day, at least 20 people would ask me where I got the shirt," Simpson says. "Nothing I ever wore got that type of reaction, so, I thought, I need to take this seriously."
He cashed in his entire $25,000 in savings and ordered 5,000 shirts. Two weeks later, he admits, anxiety set in when 80 boxes arrived and flooded his small house in Atlanta.
"I thought to myself, how am I going to sell all of these shirts?"
He and five friends set up shop on college campuses, in store parking lots and near restaurants.
"Anywhere with a crowd, we were there," Simpson says.
Within a week, sales rocketed. With a healthy stream of revenue, he rented a billboard and plastered the company's logo on it. Its social media following swelled. A flagship store followed.
Then, Reggie Wayne wore the shirt while catching a touchdown pass from Peyton Manning.
And Derrick Rose bought a hoodie for his son.
And Janet Jackson wore the shirt on tour.
The brand is gaining exposure overseas, too.
Simpson's friend, Dane Caston, says he wore the shirt, and "people were hitting us up in Indonesia like, 'Can we have the shirts? We just want the shirts.'"
Sometimes, Simpson is in awe of the brand's success.
"Ideas are worth so much more than what people can see in the beginning," he said.
Department stores and other retail chains have contacted him about putting his apparel in its stores, Simpson says, but he's worried it could dull the brand.
"I could sell the line to someone and make enough money to change my life, but I want to keep it organic," he says. "You can only find the merchandise at our store and on our website."
And he insists God Is Dope is not simply a clothing line, it's a lifestyle -- one he plans to transform into music, movies and more.
"People see hats and shirts right now," he says, "but I think in five to 10 years, they'll understand how far this movement will go."