“Love for the sinner is ominously close to love of the sin. But the love of Christ for the sinner in itself is the condemnation of sin.”

This is variant of a traditional Christian proverb; ie: "Hate the sin, but love the sinner" in Sermons, Lectures, and Occasional Discourses (1828) Edward Irving http://books.google.co.uk/books?id=VwUeH-wTxZ8C&pg=PA132, and similar expressions date to those of Augustine of Hippo: "Love the sinner and hate the sin." Gandhi did express approval of such sentiments in his An Autobiography (1927): "Hate the sin and not the sinner" is a precept which, though easy enough to understand, is rarely practiced, and that is why the poison of hatred spreads in the world.
Misattributed

Opera Omnia, Vol II. Col. 962, letter 211
Alternate translation: With love for mankind and hatred of sins (vices).

Source: The Tenant of Wildfell Hall (1848), Ch. XVII : Further Warnings; Helen to Mrs. Maxwell

Source: Letter 99, Paragraph 13. Erika Bullmann Flores, Tr. from: <cite>Dr. Martin Luther's Saemmtliche Schriften</cite>Dr. Johann Georg Walch http://en.wikipedia.org/wiki/Johann_Georg_Walch Ed. (St. Louis: Concordia Publishing House, N.D.), Vol. 15, cols. 2585-2590. http://www.iclnet.org/pub/resources/text/wittenberg/luther/letsinsbe.txt
Context: If you are a preacher of mercy, do not preach an imaginary but the true mercy. If the mercy is true, you must therefore bear the true, not an imaginary sin. God does not save those who are only imaginary sinners. Be a sinner, and let your sins be strong (sin boldly), but let your trust in Christ be stronger, and rejoice in Christ who is the victor over sin, death, and the world. We will commit sins while we are here, for this life is not a place where justice resides. We, however, says Peter (2. Peter 3:13) are looking forward to a new heaven and a new earth where justice will reign.

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 391.

De Ira (On Anger): Book 2, cap. 28, line 8
Moral Essays

God of the Sullied (2018)

Haven (1951)