The 1975 quotation (in Green’s Dictionary of Slang) is from a (British working-class) policeman, who “levelled a finger at” a man and made this accusation. My interest here is in the address term sunshine, which has become familiar to me though British (occasionally Canadian) police procedural tv shows, where the cops (or private detectives) often use this form of address, aggressively, to male suspects. From the New Partridge Dictionary of Slang and Unconventional English (ed. Tom Dalzell & Terry Victor, 2015), p. 2192:
used as a form of address, often patronizing with an underlying note of disapproval or threat UK, 1972
A (very natural) extension of literal sunshine to ‘cheerfulness, happiness’ has been around for some time, as has the extension to someone who exhibits or elicits cheerfulness or happiness, in both referential and vocative uses. Then, the address term sunshine (like any other) can be used sarcastically, aggressively, or truculently, but the conventionalization of such uses specifically in British (and not American) English, for use to men by men, especially by official authorities, is yet a further development, one that I hadn’t experienced until I got into modern police procedurals, in books and on tv.