Declan is spot on. It depends on the instruments. This other lad sounds like he had the "giant in his own mind" syndrome. When there are reeded instruments, especially Uilleann Pipes, then you would want to tune to them. The reeds are so fussy, that often the best one can hope for is for them to be in tune relative to themselves, that is the drones, regulators, and chanters in tune to themselves. But even on a "Concert D" set, they rarely are 440. Better to tune the stringed instruments to them, or as Declan points out, the melodian.

And wish your friend well, .............. as you show him the door.

Mick