1 John 4.21 is clear, The command we have from Christ is blunt: Loving God includes loving people. You’ve got to love both.
It is absolutely amazing to me that the Creator has so completely intertwined His command to love Him with all of our heart, soul, mind and strength, with the command to love our neighbor as our self. This command of God is entirely unique to Christianity among all religions in the world, now or ever.
It is because humanity is created in the image of God that He values so highly our relationship with Him and with one another. When God lived among us as one of us He perfectly embodied and fulfilled the requirement to love God and love man. We tend to choose one or the other.
Some love God and are very religious. Sometimes these people go so far as to isolate from humanity lest they become corrupted by humanity for they see God as holy, which He is, and they must be holy, which we must, in order to be with God intimately. Holiness however is a gift from God appropriated to us by faith in God Who is Jesus Christ, Who alone makes us holy through His life, death and resurrection.
Holiness isn’t something we can do but something we are given by grace through faith. We are to live holy lives because God is Himself holy. We are to be holy among people so that they will see the wisdom of such living and want it for themselves.
Others love people but have no use for God. They try and help the poor, hungry and naked but they fail to give them what they most need – hope. Those who love people only feel good about their work but fail to do work which lasts forever either in reward or result. All people will meet God in judgement and all people must be prepared for that encounter. Without loving God, we love people by making this life more comfortable for them while preparing them for a most uncomfortable eternity – one which we too will likewise join them in if we continue to not love God.
The perfect man mimics the perfect Man – Jesus the Savior. We love God by loving men and we love men because we love God and recognize that He first loved us by creating us then becoming one of us so that we can live forever with Him.