We do run up against certain limits with this way of speaking. If I say this, it would be so easy for me to implicitly (and perhaps subconsciously) mean to say something like, "love that person over there who, unlike me, is a 'sinner'!"
But what I really need is sorrow for my own sins, and sorrow for the suffering caused by sin in the world, in my own life and in the lives of others. And I need to turn to Jesus on the Cross, because crucified love is God's answer to sin and the hope of sinners.
Of course anger and aversion (i.e. "hate") are natural emotions that spontaneously arise in us as a response to evil and destructive things, as is fear. In human beings these emotions are out of whack. Even after baptism, Christians suffer emotional dysfunctionality because of the lingering range of effects of original sin. These involve not only difficulty in integrating the moral life but also the overall weakness of bodily humanity, which includes the whole misshapen neuropsychiatric "package" that we struggle with in various ways and to varying degrees.
To govern our own emotions so that they serve as a constructive energy within an integrated human response to life is a goal (in different ways) of psychological health and the cultivation of virtue (most proximately fortitude and temperance). Here perhaps we can learn some human wisdom from the discipline of nonviolence (which is anything but an escape from the struggle against evil).
We also need to recognize that "bad tempered" people (psychologically) are capable of real love (personal and moral), and that "nice" people (psychologically, again) can misuse the word and pretend the attitude of "tolerance" as a pretext for sinking into an isolated, loveless indifference.
In any case, the struggle always begins with myself. I can always reform, change, purify, and grow. I don't even know how to live from this awareness, but I know it's necessary for a real and fruitful engagement of life. It therefore brings me back to prayer, to begging for mercy.
Jesus have mercy on me, a sinner.
