And he proved, ... that there are people who care what happens to their fellow men. (Para. 15)
Meaning: And he showed, ... that there are people who are concerned with what happens to their fellow men.
Notice that in the sentence "prove" is used as a link verb, which is usually followed by an adjective or a noun. In this use, "prove" means "show in the course of time, turn out to be". Read the following examples:
Perhaps this book will prove useful later. 也许这本书今后会有用。
On the long journey, he proved a most amusing companion. 在长途旅行中, 他显示出他是一位很有趣的旅伴。
This use of "prove" is different from the transitive use of this verb. Compare the following examples with the above sentences:
He has evidence that can prove his innocence. 他有证据能证明自己的清白。
They proved him to be guilty. 他们证明他有罪。