According to the passage, ‘an act of malice’ means :--

Comprehension:

In modern times, Abraham Lincoln stands as the model of a compassionate statesman. He showed this quality not only in striving for the emancipation of the American blacks, but in the dignity with which he conducted the American Civil War. Lincoln did not fancy himself as a liberator. He thought it would be better for all if emancipation was a gradual process spread over many years. He proposed compensation for slave owners in U.S., bonds and grants for the rehabilitation of the blacks - ‘colonisation’ as they called it. But fate was to deem otherwise. The haste with which the South wanted to break away from the union with the North, compelled him to move faster than he expected, perhaps more than most men of his time had thought through the issue of slavery. ‘We must free the slaves’, he said, ‘or be ourselves subdued’. ‘Before reading, the first draft of Proclamation of Emancipation, he told his colleagues. ‘In giving freedom to the slaves, we assure freedom to the free.’

On 22nd September 1862 Lincoln set his hand on the Proclamation of Emancipation declaring that on the first day of January1863, all persons held as slaves within any state ‘shall be then, and forever free.’ Lincoln’s revolution for slavery left him without any moral indignation or passion against slave owners. The guilt of slave owners, he felt, should be shared by the whole country of North and the South for it seemed to him that everyone in the nation was an accomplice in perpetuating that system. To have whipped up any hatred against slave owners would, to him, have been an act of malice.