Does your buddy actually shoot along side of military members?
If not, why is that even part of the discussion with him?
MIL or MOA doesn't matter, except when someone in the group is using the opposite of everyone else. ^^^^ Refer to the house building analogy.
Yeah it can be done, but why?
Let your buddy try actually using a Mil/Mil optic while everyone else in the group uses the same.
Print out the reticle and explain how you dial and how you determine corrections. If you can trace the reticle on to a clear sheet and superimpose it over a simulated target, that's even better.
Make the callouts fast and make the shots fast. It won't take long to understand how it works.
Don't talk in inches, feet, yards, centimeters or meters for corrections. EVER.
The only time you should ever mention yards or meters is in LOS distance.
Then, switch him back to his rig with the MOA and hand him a sheet of paper, a pencil and the conversion formula.
Go back to shooting the same way as above and ask him to keep up.
He can't.
Going back to the discussion of military use. The government and the military in general has always been very slow to change doctrine, tactics and even worse, equipment. Between the services, some are much slower to adopt change, even when proving that the change is totally to their benefit.
Look how long it's taken to finally agree that optics (of any type) on the M-16 makes for better marksmen. Sheesh!!
The problem with adopting to change is not the troops on the front line, it's in the leadership. It's the "Well, we never had it and did fine" attitude that causes most of the reluctance to change. Add in that most of the military leadership doesn't want to take the necessary time to learn something new because it'll cut into coffee and donut time.
If your friend doesn't want a Mil/Mil optic, don't push it on him. Just have everyone else go about their business shooting and calling out in Mils.
Don't cater to him anymore.
^^^^^^^
Read that again.
Don't cater to him anymore.
Let him ride the Struggle Bus until HE decides it's time to switch buses.