(Revealing the Soul-identity, Krishna says:) I, the Supreme, reign equally in all beings. None is especially hatable or lovable for Me. However, those devoted heartily to Me, abide in Me, and I too in them.
As devotion grows, the devotee will feel more and more identity with the object of his devotion, thereby imbibing greater and greater values, virtues and enrichments, which God embodies in Himself.
By saying he has no special love or hatred for anyone, Krishna means the devotee too should have the same quality. He should be equally disposed to all, despite their behavioural variances. To meet variety is a great opportunity, nay compulsion, to outlive constrictions and grow harmony.
Samatva-buddhi-yoga is the refinement Krishna has been stressing throughout this dialogue. This is best tested and perfected in dealing with people of different dispositions and tendencies (6.9). At the same time, Krishna points that he is close to those who seek him fondly. Be close to those, who are fond of you. That is ample enough for a fulfilling life.