So the principle to "love neighbor" is also a Christian absolute of action. There are no circumstances where God would have us act unloving toward our neighbor, where love is perhaps best understood in terms of the Golden Rule, aptly summarized in the Sermon on the Mount: "In everything do to others as you would have them do to you; for this is the law and the prophets" (Matt. 7:12, NRSV). Love again is not about how you feel toward others but how you choose to act toward them both in your mind and action. And the rules of psychology are such that if you get in the habit of loving choices, by God's power and through the accountability of others, the feelings will follow.
A disposition to love and show mercy does not in itself contradict acts of justice. Such a disposition certainly requires acts of discipline. Love is not absolute permission, nor does a society that fosters a sense of cheap grace or self-aggrandizement truly show love to its members. While justice is not an absolute principle, it is the most loving way to structure a society, and exceptions to justice should be rare on the level of society as a whole, or else society would disintegrate. Sometimes love must also choose between who to be loving toward. Is it possible that love of one's own or love of the oppressed could force a nation to war or to self-defense?
Again, the Wesleyan tradition has historically been more optimistic than other Christian traditions about the extent to which God wants to empower a believer to be loving toward others. It has gone so far as to suggest that believers can be so empowered that they might very well make loving choices toward others consistently, perhaps even without exception, for the remainder of their time on earth, and do it with joy. In my opinion, it is counterproductive to spend much energy in introspection wondering whether or not we have fulfilled this expectation, as many in our tradition have done in the past. The key point is that you can indeed do the loving thing the next time such a choice presents itself, and you should plan on it!