I assume this whole paragraph is in bold (within a longer text). So, here it is:
President Lincoln is trying to reconcile his private opinion about slavery with his public duty of a president of all citizens of the United States - both slaveowners and abolitionists. As a person, he is strictly opposed to this practice and thinks that it is indubitably wrong. However, as a president, he has to act by the Constitution, which at the time tolerated slavery in the states where it existed. In a way, Lincoln admits his own powerlessness regarding so controversial an issue, with so many fierce opponents from the South.