Manchester City star Sterling came in for heavy criticism from some quarters for having a tattoo of a gun on his leg, while he drew further flak after it was revealed he arrived late for the team's training camp.
However, after receiving the support of the Football Association as well as team-mates Fernandinho, Kyle Walker and Danilo, Sterling got the nod from Southgate when he was named in the England boss' first XI at Wembley and produced a lively display, although it was somewhat tainted by a yellow card for diving.
Speaking after first-half goals from Gary Cahill and Harry Kane secured a 2-1 win, Three Lions boss Southgate suggested the negative headlines had made it an easier decision to pick the former Liverpool forward.
"I had a decision to make on whether to play him after turning up late, but actually that wasn't a decision once he started to come under fire from every other direction," he said.
"The most important thing I do over the next six weeks is protect the players and [make sure] they respect each other and they understand how important it is that we support each other and work together.
"You've always got to balance as a manager what's the message to the rest of the group and what's most important at that moment in time, so the situation was one we didn't want to happen, don't want to see that happen again, but I think from my point of view was the best way to deal with it on this occasion.
"So in terms of his performance I got the level I expected. With forward players there will always be moments where the ball is slightly the other side of somebody or taking somebody on isn't always going to succeed, and there were a couple of those, but in general I thought those front four played really well."
On Sterling's booking for simulation, which came after he took a tumble in the box under apparently minimal contact, Southgate added: "It looked a very tight call from where I was sitting because he was travelling at such speed."