We are commanded to love one another, in the Bible. It's been claimed that this injunction distinguishes Christian ethics from others. That may be true. I wonder, though, whether that is to its credit. That is to say, I wonder whether this command can be followed. If it can't be in most cases, that would seem to make loving one another an unrealizable, and therefore useless, ideal.
I would maintain that it is an ideal that certainly has not been followed, by Christians or others, except in individual cases which themselves are distinguished from others as being romantic or familial in nature. A parent (normally) loves his/her child. One person may be in love with another. But nobody loves a neighbor, or acquaintance, or enemy, or anyone but one's child as one loves one's child, nor does anyone love anyone but one's lover as one loves one's lover. It would be dishonest to claim otherwise.
It may be asserted that the command that we "love one another" is not a command that we love all others as we love our children, or as we love our lovers. And it's true that another Christian injunction is that we love our neighbor as we love ourselves. It's not clear to me, though, that we can love ourselves as we may love others. We have no relation to ourselves, unless we subscribe to a dualism odder than most. However, we necessarily have relations to and with others, for the excellent reason that they are other. And just how do we love ourselves that can be said to apply to our love for others?
If what is intended by "love" one another is that we feel benevolent towards each other, or seek each other's good, then it seems to me we're not referring to "love." We're referring to being nice, or fair, or helpful to one another. We will be nice to those we love, of course, but we'll be much more than that as well.
An ethics based on love would be wonderful, but it is fantastic; so remote from what is the case that it cannot be achieved and is not applied. If we seek to be moral, we should set standards which can be achieved. Any realistic ethic must be based on such standards.
We can, for example, respect one another without having to be dishonest regarding our actual status and feelings. We need not love someone to have respect for their person, thoughts and desires.
Those who enjoin us to love one another do us, and themselves, a disservice. They urge us to do something we will not and cannot do. Especially when such an injunction is portrayed as a divine command, this can lead us to disregard what is within our capacities which can guide us in our conduct.
To paraphrase Mencken (and refer to him once again) love is the triumph of imagination over intelligence. We can imagine all we want, but we will address our problems only through the application of our intelligence, because intelligence is part of our interaction with each other and the rest of the world. Imagination may inform intelligence, may encourage us to be creative in our intelligence, but that is all it can do.