You know I would. But seriously, milsim is milsim because the players try to immerse in / simulate this military thing and for that things like this do matter. If the fat guy gets the order to patrol the area and can't climb up the hill, or he can't climb into the APC or there are tiny soldiers shouting like on a playground that will ruin the game. That's the same as not allowing high caps, or face masks.
On an average skirmish, everyone is a spec ops operator. On a milsim, you are infantry. You don't need to do 1000 press ups, but you might need to carry your mate.
Don't get me wrong, I respect and welcome kids on normal airsoft events, it's just about the milsim.