Greg Lestrade put up a lot to have Sherlock Holmes provide his insights into the more difficult crimes scenes, one of which was being told consistently that he was an idiot. Having Sherlock around, always proving his thought processes wrong and being put down on a regular basis was a humbling, if not irritating, way to spend many of his days. It certainly wasn't helping his level of confidence.
However, despite Sherlock's accusations against his intellect, Greg was not a stupid man.
"Go on then," he sighed with only slight amusement, mixed with exasperation, when Sherlock mocked that there was plenty of clues to pinpoint the shooter. The detective consultant had almost died, and Greg figured he could at least give Sherlock his shining moment...though you'd think he'd be content with the many shining moments he had daily.
As he talked, Greg tried hard to hide the genuine smile that threatened to break through. "But not just a marksman, a fight. His hands couldn't have shaken at all clearly he's acclimated to violence," he was explaining proudly, thinking he was showing off. "He didn't fire until I was in immediate danger, though, so strong moral principle." Greg nodded along as if he didn't already have a name in mind while Sherlock's mind worked out catch up to his brilliant deductions. "You're looking for a man probably with a history of military service…"
Sherlock's voice began to trail, and from the corner of his eyes Greg could see Watson standing outside the boundary of crime scene tape. Again, Greg had to force himself to keep from smiling at the obvious answer, and at the sight of Sherlock's realization.
"And nerves of steel…"
Then he was backing down, stating the didn't actually know who could have shot from the other room to kill the cabbie, and Greg put up a weak offense at his denial. Sherlock said he had better things to be talking about, claimed he couldn't think properly because he was in shock, and then headed off to where the shooter stood.
This time, Greg did allow himself to smile. If John Watson could make Sherlock declare ignorance, going against his pride, then there certainly was something special about the detective's new flat mate. His smile widened as they walked away from the crime scene, side by side, trying to keep themselves from laughing at whatever joke they shared...and failing.
So, no, Greg Lestrade was not as stupid as Sherlock would have liked to think otherside. But, being quite intelligent, Greg knew that the best course of action was to keep his mouth shut and just watch with a bemused smile as Sherlock strutted home with his new partner by his side.