It is possible to hold love for everyone, in any situation, regardless of the circumstances. Of course no one is perfect and so just because something is possible does not mean it always occurs. But this is not the point.
The point is that the origin of morality is love. In the absence of the experience of love, it is possible to approximate the correct behaviours to imitate it, but it is a pale and brittle imitation of real love-derived action and most often descends into immorality under pressure or nuance.
The modern justice system is a fantastic example of this. It doesn't work in any but the most extreme cases - and even then there is an argument to be made against it. Locking people up like animals doesn't improve society or help the offenders. It provides a temporary relief to victims but even that is hollow. Punishing children has been repeatedly shown to be ineffective for correcting behaviour. Why we think adults are different is a simply a lack of love.