[Blarg]

It's not disrespectful. People from times before his never called each other by their first names in office settings, etc., if it was a particularly formal office. The polite way to speak to someone was using a Mr. or Mrs. or Miss in front of their last name, or the later Ms. This was done without class distinction.

Calling people by their last name alone became more commonplace, but it was informal, and it was never used with one's superiors. Class distinctions began to be made more and more in conversations over the years, until now the use of "Mr." has vanished for inferiors, and they are addressed by their first names. Unfortunately, this loosening didn't go both ways, and we are actually less egalitarian than we were: superiors retain the Mr.

Calling people by their last name alone is an informal thing, but anything informal can be inappropriate in formal circumstances, and thereby used as an insult in formal situations. It sounds like your death metal friend is merely practicing being touchy, unless your office is quite formal and peers normally address each other with a Mr. first.

There's a lot to be said for tone, too. Some of it might have been a "you hadda be there" thing. Maybe it was more the presentation than the event.