Lincoln's views on his mother's ancestry

[Sally]

Yesterday, on C-Span’s American History TV, I saw a lecture given by author Stephen Mansfield, who wrote “Lincoln’s Battle With God.” His lecture (and, presumably, his book) outlined the various phases of Lincoln’s religious beliefs. He talked about how Lincoln was deeply ashamed of his mother’s illegitimacy and that during his atheistic phase he referred to her as a “bastard”. Mansfield also stated that Lincoln believed his remarkable intelligence and insight had come to him from his mother, who had inherited them from her Virginian aristocrat father. Thus, he was “cursed by Job” and all his intellectual gifts were shadowed by sin and shame. According to Mansfield, these stories of Lincoln’s feelings about his mother had been related by William Herndon.

I’d never heard this before. Have other Lincoln scholars or biographers come across convincing evidence of Lincoln’s true feelings about his mother’s birth, or are Mansfield’s claims based solely on Billy Herndon’s memoirs?