seems an odd rule for a place where shooting is the point. but discussion at tam's centered around exactly that rule at the range she frequents. there they require bringing in unloaded/cleared firearms only...necessitating what she and shootin' buddy point out is the distinctly dangerous practice of unloading range guns as well as carry-ons in the car or parking lot, etc.
but as i said in comments there, that same logic holds for any place with such a rule. and there are many, sadly including even most gun shops, which often feature a big sign on the door; "no loaded firearms". that made a bit more sense in the days before carry permits and most guns coming in the door were for sale, trade, repair, etc...but now, with perhaps a majority of those who frequent ffl's carrying concealed, it has become an absurdity...and a decidedly dangerous rule. combined with the many places -public and private- that ban loaded firearms on the premises, it brings into focus just how often the need for permit holders to unload -or offload- their weapon in the car before they can enter these premises unnecessarily endangers everyone in the vicinity, as manipulating mags, slides, and cylinders requires much touching. and though some anti's would have you believe the very presence of guns can cause random carnage even when they're safely in their holsters, it's all that touching that can result in an n.d.
it's a big problem that many don't really think about, and there's not an easy solution...maybe the best one is to just avoid such places whenever possible.