Learn Perek 32 of Tanya. If you think of yourself as a body in which a neshoma rests, then you will consider everyone else the same way, and in that case you can’t love every Jew, because some Jews’ bodies do very ugly things.
But if you first think of yourself as a neshoma, literally a part of G-d Above, that happens to currently be resting in a body, then you will think of others the same way; and when you see a Jew whose body does wrong you will love him all the more, and feel sorry for him, trapped in such a situation and unable to influence his body to do better.