How was lincoln able to reconcile his reverence for the founders?

First, he admitted the bravery and the intellect that the founders had to be able to bring independence for United States.
That's being said, Linocl had several difference with the view of the Founders. Regardless their sacrifice to establish this country, we can't deny that the founders allow the ownership of other human being as property in the constitution and he believed that united states could only achieve true liberty if it no longer restrict other humans' liberty in the process.