You have asked a great question Yvonne. Hawthorne has both made an observation about Hester Prynne and a jab at the Catholic church. The speaker slams the Catholics with the opener:"had there been a Papist among the crowd of Puritans." The speaker is saying that a Catholic would be taken in by the outward beauty of the subject before him, namely, the attractive Hester and baby, Pearl. This is significant because, it lines up with the second quote which says:"but only by contrast, of that sacred image of sinless motherhood, whose infant was to redeem the world." The speaker juxtaposes the image of the shallow Catholic versus the clear-headed Puritain, and then, the soiled Hester whose child is tainted by her sin, versus the virtuous Madonna and the spotless Christ-child.
A follow-up question might be: Who is qualified to judge Hester and her child, or anyone else?