I commend you for doing that to a degree however, we aren’t check airmen and it isn’t our job to do it. If it was then we would all have an extra fed ride and be qualified to teach, but we aren’t. When a line captain starts teaching in the cockpit unprovoked, it will come across as an insult in most cases. Chances are, this is exactly why those guys roll their eyes. You’re basically telling them that you automatically assume/believe they have no knowledge of anything and are weak.

It is my experience that some guys do have a decent understanding of performance but most have almost none. Heck some that come out of the training center don’t even really know what they’re looking at with the TPS besides what speeds to plug into the MFD. I’m always more than happy to answer anyone’s questions or provide assistance to understanding topics for those who want to learn. But I will never just start teaching to someone who hasn’t asked first.