Also, how do you know that he's not just trying to get into a different shooting style than you? The stuff you would take on a deer hunt might not be the same stuff you'd take to a Magpul carbine class. Similarly, the rifle and pistol you would use in Cowboy Action would not be the same as a tactical class.
Gear does not make one a "mall ninja". It's not knowing how to use it that makes you a poser. If you bought a molle vest and let it sit in you closet, or put it on to goof around at the range, you might be a mall ninja. Of course, being an adult, you're free to have fun how you want as long as it's safe. But if you took that vest to a tactical carbine class and actually learned how to use it for magazine changes and such, would you still be a mall ninja then?
I find it odd that we have people who spend thousands of dollars on civil war muskets and clothing for reenacting, or on lever action carbines and SAAs to go to Cowboy Action shoots, and all of that is seen as perfectly fine and dandy. But when an adult has more fun spending their money on modern military gear, as opposed to 1860's military gear, he's considered a moron.
OP, if your buddy bought a Henry Repeater and a SAA would you try to dissuade him? If he bought a civil war uniform, mess kit, grew a mustache and joined a Reenacting outfit, would you consider him foolish?
Or would he just be an adult spending his money on interests that are different than yours?
*I have an Army buddy who has probably sunk close to $20,000 in WWII guns and gear. He has a complete 82nd Airborne outfit with weapons, as well as an SS uniform (he's not a skinhead, just a history buff). He takes part in WWII reenacting a few times a year. I on the other hand don't own a single firearm that has a wooden part. And yet, we get along fine. I don't tell him not to spend thousands of dollars on WWII stuff or wood stock guns from the 40's, even though they don't appeal to me in the least. He's an adult and can spend his money on the things he likes. And he can do it without getting attitude from me about what I think is better.