This guy sounds like a complete d**k.
Apart from the fact that a "traditional" musician would only ever have tuned by ear, and unless gifted with perfect pitch, this is the biggest lot of drivel I have ever heard. I bet this guy would also tell you that you were playing tunes "in the wrong key".
Even the most "traditional" of traditional musicians would recognise that if you're in a session situation, you tune to a common standard. Otherwise you're just out-of-tune. "In-tune" is not necessarily in-tune to concert pitch, most of the time, we settle for in-tune with one another.