The second reason is that all Israel constitute one lofty portion chosen from mankind to be G-d's unique and holy nation. Being this way, they were marked by G-d for special affection. They alone are called "adam," because they took the place of Adam, the first man, as standard-bearers of G-d's mission here on earth. Since all Israel constitute "adam," ans were created in G-d's image and chosen to be His firstborn, it is a special mitzvah to love every Jew, assuming he shares our commitment to mitzvot and to serving G-d.
Surely man's having been created in G-d's image is the most important factor here. Whoever was created in the image of the King bears on his person the glory of the King, Himself. whoever ridicules him is ridiculing G-d, as it were, and who would dare to do such a thing? Nonetheless, there is no need here for a positive act of love and respect. All that is required is a prohibition against degrading, cursing or otherwise harming anyone created in G-d's image, as long as he has not become an enemy of G-d.
Nonetheless, from the moment Israel was born as G-d;s holy elect, the mitzvah of loving and respecting every single Jew was born as well. Every Jew, besides having been created in G-d's image, was also chosen to be part of G-d's special people.
It follows that there are three types of human beings, and each must be related to differently.
The first is the Jew who shares our commitment to mitzvot. It is he we are required to love and respect via G-d's command to "love your neighbor."
The second is the non-Jew who was created in G-d's image, yet who is not dear and special to G-d and not classed as "adam." After all, Adam's mission in the world passed on to Israel. Although we are forbidden to hate or denigrate such a non-Jew as long as he does not become an enemy of G-d and as long as he keeps the seven Noahide laws, there is no mitzvah to love and respect him.
The third is the person, even a Jew, who becomes an enemy of the Jewish People. It is permissible, and even a mitzvah, to hate and degrade him.
All the same, as long as a Jew remains on good terms with G-d, His mitzvot and His teachings, it is a supreme mitzvah to love and respect him with all our heart and to make great sacrifices for his sake in order to save him and help him. (Rabbi Kahane, Ohr HaRa'ayon on Love and Respect for One's Fellow Jew pp.225,226)
We were slaves in Egypt, redeemed by Hashem to be slaves unto him. We don't have the right to hate or love whomever we choose. We must control our emotions and follow the halachah. There is an appropriate time for hate, love and indifference.