Read this excerpt from allen ginsberg’s "a supermarket in california." i saw you, walt whitman, childless, lonely old grubber, poking among the meats in the refrigerator. why does ginsberg make an allusion to walt whitman in this excerpt?

I would say Ginsberg makes an allusion to Walt Whitman in this excerpt to suggest a familiarity and kinship with Walt Whitman and other outcasts.
As you can see in the poem, Whitman is all alone, wandering around the supermarket, searching for a soul mate. He asks the poet, 'Are you my angel?' suggesting that he has no one else around him, which is something the poet can relate to.

Go to school and learn fool