Richard Hays in The Moral Vision of the New Testament, (p202) gives three reasons why "love" is inadequate as a unifying theme for NT ethics (and by implication why it is inadequate for ethics today).
1. Mark, Acts, Hebrews, and Revelation "resist any attempt to sythesze their moral visions by employing love as a focal image . . . Despite the powerful theological uses to which the motif of love is put by Paul and John, that motif cannot serve as the common denominator for New Testament Ethics." Instead Hays suggests "community, cross and new creation."
2. "What the New testament means by love is embodied in the concretely in the cross." and so to treat love apart from the cross is to result in "conceptual abstraction, away from the specific image of the cross."
3. "The term ["love"] has become debased in popular discourse; it has lost its power of discrimination, having become a cover for all manner of vapid self indulgence." "We can recover the power of love only by insisting that love's meaning is to be discovered in the New Testament's story of Jesus - therefore, in the cross."
So who do you believe, Hays or the Beatles?