Read some of his writings. He talks about his disgust of slavery and desires for emancipation for decades prior to his presidency. In addition, the fact that they manifested themselves at "convenient moments" only serves to prove his political prowess and ability to navigate those politics during the most divided time in our nation's history.
Regardless, his actions stand on their own.
He subscribed to the idea that African Americans would have a better life in Africa than in the United States under the circumstances of the day. He never subscribed to mass deportations...And, yes, it's true that Liberia was founded before Lincoln, but that does not change the fact that Lincoln subscribed to deporting blacks.