How can I love everyone else as I love myself? I don’t believe that I can love Hitler as I love my family.
We must first distinguish between two very different kinds of love. The love you have for your family is more aptly called affection. As affection often depends on the feelings, it would be almost impossible to summon affection for someone who is known to have committed horrendous crimes against humanity. A love that is dependent on feelings is not the Christian love to which we are called.
Christians are called to what is known as agape: a love based upon the will and that desires for the other that person’s ultimate happiness, the ultimate happiness of every human person being God himself. In other words, we are called to desire salvation for everyone, regardless of our personal feelings toward them. A Christian can and should despise Hitler’s crimes while still hoping that he died repentant of those crimes and found salvation.
In short, Christians are only called to desire that all men be saved, not to have affection for all men regardless of whatever foul deeds they commit.