It makes it a little easier to love the sinner and hate the sin if we can separate the two a little bit in our minds. Thus we can keep hatred from running away with us. Another way in which hate runs away with us is it keeps us from seeing clearly. We tend to see only negative things if hatred becomes too strong with us.
If someone posts something on the internet that we disagree with, we tend to launch out and attack it. Yet that same person could post positive things, and we’ll just skim over those and click onto the next thing. We’re only focusing on negative things. Only negative things grab our attention. We all find negative things easier than positive things. Can’t we spend a fraction of that time promoting good things, too? We have to remember while hating evil that we must also love the good.