For the mainstream of the Catholic intellectual tradition, love is not primarily an emotion, but an act of the will. To love, Thomas Aquinas says, is to want the good of the other. Consequently, hatred is not primarily a feeling, but desiring evil for another, positively wanting what is bad for someone else.
He goes on to draw exactly the kind of conclusion that I lament ina long, impassioned post I wrote on this very subject a year ago.
to criticize someone for engaging in immoral activity is not to "hate" that person. In point of fact, it is an act of love, for it is tantamount to willing good for him or her.
This is wrong, or at best misleading. The pharisees were famous for criticizing people for engaging in immoral activity, weren't they? They were also famous exactly for their lack of love. In truth, to criticize someone for engaging in immoral activity may be an act of love, but it may not be. It may be, and very often is, an act of contempt or indifference or neglect, all opposites of love. Everything depends on our interior attitude toward the concrete person in question. Do we see and care about him as an individual? Are our criticisms genuinely motivated by real concern for his wellbeing? Or are they rather more like a defense of the objectivity of truth and the superiority of our moral vision? Do we treat him as precious and beloved, or mainly as an exemplar of immorality and disorder?
One reason we are so often accused of bigotry and hate when, say, we oppose same sex marriage, is because our mode of opposition has all too often conspicuously lacked love.
I'll end with the same lines from Jean Vanier that I used in that post from last year. They offer a much better definition of love than "act of will."
Loving someone does not simply mean doing things for them; it is much more profound. To love someone is to show to them their beauty, their worth and their importance; it is to understand them, understand their cries and their body language; it is to rejoice in their presence, spend time in their company and communicate with them. To love is to live a heart-to-heart relationship with another, giving to and receiving from each other.