How is it possible to love a sinner?
One of the Hasidic answers is derived from the verse "Love thy fellow as thyself."
A person is to love others just as he loves himself despite his intimate knowledge of his own imperfections and flaws and even though he may simultaneously hate himself for them.
We find this idea expressed in the verse "Love covers all sins (Proverbs 10:2.
Love does not conceal facts–rather, it changes the evaluation of those facts.
Although a person recognizes his own sins,his love covers them over and mitigates their severity and hatefulness.
In that sense,"Love thy fellow as thyself" is the challenge to see another as one sees oneself.
It is not that one does not see the sin – but one sees it from a different perspective,and then one's entire attitude toward it changes.
–Rabbi Adin Steinsaltz
from Understanding the Tanya Chapter 32, p.135 by Rabbi Adin Steinsaltz