"What man has made of man" is one of the most striking expressions in the poem "Lines Written in Early Spring." It describes Wordworth's feelings and thoughts about human activities against nature. What made the poet think so?

The poem "Lines Written in Early Spring" is notable for its juxtaposition of the harmony of nature with the villainy of mankind. The flowers enjoy the air they breathe, the birds take pleasure in each little movement, and the buds on the trees delight in the spring breezes. As the speaker sits outside in a grove, he feels the peaceful brotherhood of living things that exists in the flora and fauna, and he ponders the connection between nature and man. Since mankind, too, is a product of nature, the relationships between humans should be as serene and cooperative as the relationships among birds, trees, and air. But the speaker realizes with regret that this is not the case. Thus he contemplates "what man has made of man."
Wordsworth wrote this poem in 1798. In the preceding decade, he had ample opportunity to observe the negative effects that some people had on others. Although he, like many early Romantics, viewed the French Revolution as the harbinger of a golden age, he was bitterly disappointed with the bloodshed and war that followed. The conflict affected him personally. He had been traveling in France in 1791 and fell in love with a woman named Annette. When their child was born, he intended to marry Annette, but he had to return to England due to financial difficulties. He planned to return, but war broke out between England and France, preventing his reunion with his daughter and her mother.
Did Wordsworth have such interpersonal and international conflicts in mind when he hinted at the "sad thoughts" he entertained that lovely spring day? Probably. Yet every person knows well enough firsthand "what man has done to man." We have all seen people hurt each other on small and grand scales. Like Wordsworth, we can wish for a harmony to exist among people that is akin to what he observed among the elements of nature on that placid day in early spring.