We could just stop the person from killing everyone. Maybe send him to an island or lock him away. Whichever way you look at it, loving everyone can be a tough job especially if not everyone else is the same. Having to protect people from the injustices of others can make me look like I do not love the person I am stopping from being mean.
The recent wars were examples of not loving foreigners as much as we love our own families. They became statistics....some faceless enemy....we cheapened human life by killing them so easily (without a thought to their worth as human beings).
Remember, God said "thou shalt not kill." Also you have to remember that God considers all humans to be his children, and we are not supposed to kill the other children of God.
Arnold Schwarzenegger tried to do that (love everyone). In fact, the maid's son is the spitting image of him.
True love doesn't involve just satisfying lust (though those in love satisfy every aspect of their lives with each other). The caring that we have for all of society is very special.
I see kids come out of a Catholic church, then toss candy wrappers on the ground. Sure, it's pollution, but it is an even worse type of pollution....pollution of the soul. It means that they don't care enough about other people to keep the world a tidy place.
To hate is to judge.
"Judge not, lest ye be judged" (Jesus, Sermon on the Mount).
Yet, if we don't judge God and Jesus, we would not judge them to be good and wholesome. If we don't judge the devil, we won't recognize him. If we don't judge someone who is "fightin' evil" we might mistake them for a righteous man, rather than a tool of the devil who makes wars against innocent nations.
We, therefore, have to judge, in our own hearts, but just not bad-mouth others publicly. For example, when President W. Bush called various Iraqis names (Dr. Evil, Dr. Death, et al) he motivated wars against them, and that killed perhaps a million innocent Iraqi people (some were innocent women and children). Of course, that also involved "bearing false witness" (taboo under the 10 commandments).
If we don't judge others, we follow them, and that harms others (it is sinning).
The ability not to hate someone is also the ability to ignore their crimes, and to aid and abet them in further crimes.