Why did Albert Barnes say slavery was wrong, even though it is found in the Bible?

Barnes attracted attention during the 1829 evangelistic campaign: in a sermon entitled The Way of Salvation, he rejected the doctrine of original sin and stated that human is a morally free person, free to accept or not accept Christian salvation. Developing and implementing the idea of the New School about spiritual revival, an idea that began with the Second Great Awakening, Barnes at the same time convinced the New School presbyterian that personal revival should entail an active public position. Accordingly, he took an active part in a number of movements for reform, in particular, for the Prohibition and the abolition of slavery.

Explanation:

supplies had to travel a long distance across water on ships that were often attacked, so they did not reach europe