This is a quotation taken from the writings of Venerable Louis of Granada (Summa of the Christian Life, Volume 2 pg 28, translated by Fr Jordan Aumann published by Tan Publications):
The gift of knowledge represses anger which is usually accompanied by folly, as it is written: "Be not quickly angry, for anger resteth in the bosom of a fool."1 He who has the gift of knowledge understands that he must not be angry at those who have unjustly offended him, but must treat them as one treats children, the sick, or those who are mentally ill. Thus, parents, friends, and doctors are the objects of much abuse and recrimination, but they suffer it all with patience, and will even endure much more until the sick have regained their health or the demented have been restored to sanity.
1.Eccles 7:10
Obviously this helps one to take a compassionate/patient view of the sinner’s faults and failings (rather than condemning the sinner).
I would also highly recommend the book The Hidden Power of Kindness written by Lawrence Lovasik which helps one to realise that the faults of others are due more to probable ignorance than intentional malice.
God Bless