If you read the discussion below there is one aspect I didn't bring up in this post. What does the rest of the team do when you get challenged? Do they stand up for you and defend your decision and your right to make the decision?
You brought up the post mortem. That was your decision to make, not only did you get challenged, but you also had to bring in your manager. What did the rest of the Team do? I have a hard time imagining a scenario, where you make a decision, where everyone but one guy goes against you and you still need a manager involved.
>This is incorrect. They actively seek guidance from me regularly. As I mention in another post, three engineers joined the team specifically to work with me. I don't have doubts about this.
I don't doubt any of that. And they may very well respect you, but that does not automatically translate into them respecting you as a leader.
>What's the point?
I gave you an outsiders perspective. Even if I am wrong about everything, the one thing I am absolutely certain about is that this one engineer sees you as a failure in leadership. And if he sees you as a failure in leadership (and has at least some positive opinions about his teammates, if he doesn't you are in far deeper trouble with him) then he must believe that the rest of your team does not believe in your leadership either. If I am wrong and the rest of the team stands firmly behind you, then you only need to show him that.