In all seriousness they shouldn't look down on air rifle shooters as shooting an air rifle teaches you to be a better shot, particularly a springer.
I've shot centrefires and shotguns for over a decade now and recently rediscovered my old Webley Longbow.
I am currently between .22LR rifles after getting rid of my old one and being stuck in the variation time warp, I dusted the Webley off and took it down to the rifle club.
A springer really punishes any lapse in technique as the pellet hasn't left the barrel before the recoil starts and is great for "unlearning" the bad habits you accumulate in years of CF shooting.
Taking the piss out of mates who shoot air rifles/Centrefires/shotguns/nerf guns etc is fine and in fact something I enjoy personally but if someone is being arsey then just point out the above.
"An infinite number of monkeys banging away at type writers for an infinite period of time will eventually reproduce Hamlet" Thanks to discussion forums we now know this to be untrue.