Not all of these people would react to this quote in the same way. In general, Sumner would have approved of it much more than Rauschenbusch or Paul would have.
Alice Paul was best known as a suffragette and a leader in the women’s rights movement. She might not have disagreed with the statement, but she would not have agreed with its spirit. She would have pointed out that it only referred to men, not to women. She would have said that this undermined the country’s claim to be a land of opportunity. Rauschenbusch would likewise have disagreed. He would likely have pointed out that the rich had too much power and did not allow others to have a true opportunity to advance. He would have advocated reforms that encouraged people to be more humane to one another. He would have said that the capitalist system was too brutal and that it drove people to compete with one another instead of cooperating. We was a major proponent of the “social gospel” which called on Americans to live together in brotherhood and to treat each other as Christians.
By contrast, Sumner would have been more likely to approve of the statement. He would have said that the US was a land of opportunity. He would have pointed out, however, that it could only remain that way if it were to keep its policies of laissez-faire so as to allow the cream to rise to the top.