If we can identify the sin and keep ourselves positively pure, we will more easily be able to forgive. As long as we maintain enmity towards a sinner, forgetting the supreme cause, we share in the blame. By contact through consciousness, we are infected with that same fault. Only sadhu-sanga can free us from our own mental traps. By following the spotless path of the great acaryas and seeking out sadhu-sanga, we can make solid advancement on the path back of bhakti, and experience increasing love with melting hearts.
Devotion is ultimately a matter of the heart.
If we examine our own hearts first, we will understand others better.