Check out this wild video of a guy literally going behind the checkout counter at one of these drug stores in the Richmond District of SF -- where these types of smash and grab thefts have become all too common ... with little to no resistance by anyone there.

Per usual, the dude is having his way back there ... snatching up whatever he can and throwing it in a bag, all while the staff standby and call 911 right next to him.

However, this time ... it looks like somebody was sick of playing bystander and wanted to get in the mix a bit, to at least let the thief know -- hey, this isn't cool ... and also, screw you! And so ... they got into a food fight of sorts, with fruit being the first weapon of choice.

The crook and customer trade banana blows, and eventually ... the former throws what appear to be cookies before getting out of Dodge. It's kinda funny, but also surreal.

BTW, this is far from the only incident like this that's occurred at a Walgreens -- not just in the Bay, but across the country it seems ... as thieves seem to have figured out the retail giant will literally not do a thing to stop anyone, as it's against their shoplifting policy.

All they'll do is call the cops, but by the time they show ... a lot of these folks are long gone. Even the hired security guards have orders not to interfere -- and it's becoming untenable, as Walgreens has recently announced mass store closures, citing these hits as a partial reason.