What are your "best practices" for handling disrespectful, too comfortable subordinates?

When I commissioned out of the enlisted ranks, I wanted to make sure I stayed humble. I was the first to admit that ensigns were noobs, and that there was nothing about my rank that granted me or my ideas some high status. "Hell," I joked once on my first week aboard to my division, "I still need directions to find the head."

Although good in a lot of ways -- folks came to me with problems I don't they would have otherwise -- there were huge setbacks I struggled to handle. Over and over again, my presence would make my Sailors get *very* comfortable in how they spoke to me. I once had an argument with one of my E-6s after he explained to me how he decided whose orders he followed. In his logic, he didn't actually have to listen to someone unless they were simultaneously older, higher ranking, paid more, and had been in longer. Miss one of the blocks, and he doesn't really have to do what you say. Again, Ensign Me actually allowed this to become a debatable back and forth until it occurred to my LCPO that we could be heard on the other end of the barge.

Now I teach leadership and ethics at an NROTC Unit, and I tell these tales to my midshipmen as "what NOT to do". It's not a problem for me now because, frankly, I know what I'm doing, but I still get the cocky Sailor who decides to debate the merits of rank with me. How do you folks handle these things (i.e., your people growing so comfortable with you that they cross the line of professionalism and start explaining how they don't *actually* have to follow your orders)? Shake your head and walk away? Blow up on them? Respectfully explain the concept to them, but chance allowing it to be a debate when it is, in fact, not up for debate? I've found my own path forward, but I wanted to hear some thoughts from this community that I might take back to my midshipmen as "diverse words of wisdom".