Because he became that person and filled that role. In 1863, Lincoln would set over four million people free. But he arrived at that point through a long, sometimes convoluted, process. If Lincoln was truthful in 1858—and many historians believe he was—then he was, at that time, a rather typical man from the Western states. He did not dislike black people, and he thought it a terrible thing that they were enslaved, but he had no black friends and no basis for comparison.