The idea is that universal love for all people detracts from one’s particular loves for those near and dear to him.
Therefore, this matter must be rightly understood. Universal love is connected with natural law. Natural law, again, proscribes doing evil. Every man, no matter what sort of person he is, has natural rights, such as to walk the earth, not to be assaulted or robbed or defrauded; you know, the usual libertarian-Rothbardian rights.
Particular love, on the other hand, regards the doing of good. The world is constructed in such a way that with few exceptions, we can only do good to ourselves and those closest to us. (One such exception is teaching economics, because by doing that, one seeks the common good directly; here the particular and universal coincide.) So, to aid our clan, we plot and plan as best we can. But in doing so, we do not step over the dead bodies of our fellow men.
Universal love then has two aspects. First, you do not violate anyone’s natural rights in your pursuit of your own personal good. Second, in your heart, you remain a well-wisher, maintain good will toward all, and never indulge in misanthropy or cynicism.
Thus, universal love does not entail non-discrimination. I can privilege my own children; I can choose my family, friends, neighbors, and associates.
Suppose some blacks have moved into your community. “There goes the neighborhood,” you say. Is this unloving? Not at all; we all know that blacks bring with themselves crime and lower property values. They ruin vast stretches of real estate. And acknowledging truth can never hinder charity. It is true, however, that lupus est homo homini, non homo, quom qualis sit non novit, “A man is a wolf, and not a man, to another man, for as long as he doesn’t know what he is like.” If we were to get to know blacks, and give them every (privately extended) help, perhaps our love for them might grow.