Hasty generalization, if I'm correct, is synonymous to "jumping to conclusions." So you could say something that has to relate to jumping to conclusions and not judging a book by its cover. For instance...
"As her sky-high heels clicked against the pavement, I watched her shiver against the overbearing chill in her unfitting cocktail dress. There was no way she was off to someplace morally just."
Obviously, the speaker made some prejudices about the girl because of her short dress and heels. Should you choose to use this example, you could elaborate on how the girl could have been going home from a party, or couldn't catch a cab, or maybe the dress was the only clean piece of clothing she had left. Things like that.
The lines suggest a feeling of calm, of being transfixed by the light dropping through the tree branches. The poet creates this feeling first with the setting, “Under the trees.” Then, the phrase “a green/latticework of branches” compares the broken pattern of light to the crossed patterns of tree branches. This suggests a peaceful setting. He finishes the stanza with the image of the light as“drifting down like clean/white sand.
The /s/ sounds in “cicada sends/ its sawing song” suggest the repetitious, raspy noise of a cicada itself.
Yes, the poem expresses an appreciation for how light enhances the beauty of sights and sounds in nature.