Love is one of those words that seems to take on a lot of meanings. We "love" our spouses, children, family, friends, god, cars, TV shows, movie stars ... I just love it when people say "I love my friend BUT..." Is that really love when you have exceptions? Then look at Jesus' words. Does he really expect us to have the same feelings for Hitler we do for our spouse or God?
The only thing in common is that you care about everything that you love. Obviously you care to different degrees. I love my kids. Sometimes they do bad things. Don't feel the strong affection that is associated with love at those times. But because I love my kids, I don't want them hurt. I want their bad behavior corrected if possible and I want to keep them from hurting others, but I don't want harm brought to them.
I want the kind of love that I have for my kids to be applied to EVERYONE, even people that are horrible. I think it is horrible to rejoice in the death of anyone. Sure it has to happen at times, but it would be much better if we could avoid it. I think it is more true to Jesus' words if we lived that way and I agree with his logic.