I agree, private security firms are dumb, but i also don't expect some schlub making like 30 grand a year to physically intervene to deal with a guy who could very well be packing heat in a pharmacy over a bunch of stolen toothbrushes when cops are pulling down three times that.
What's the point of having them then? To call the cops when a robbery happens? Couldn't a cashier do that?
He could have at least tried a little harder to take back the stolen merch, as in tried at all.