Ya gotta love a site where opinions that range from “it’s a shame to see it hanging out in the weather rusting away” to “lets throw rocks at it” can peacefully co-exist.
I’d suggest just don’t throw rocks at the shop owner if he doesn’t want to sell. Presumably it is his bike and property to do with as he likes. It is not the rarest or finest of the herd by any stretch, and there probably isn’t much he could hang out there as advertising to attract more attention to his business. The attention it gathers up there growing a bit more patina day by day may ultimately save more similar bikes than if he polished it, kept it in his living room and rode it a couple times a year.