Killing animals, plants, micro-organisms is also secondary, however, hurting a human being is more severe act.
What makes it any different to kill one kind of animal (humans) from any other? Since we know of many animals who experience pain, suffering, and consciousness like humans do, this seems to be nothing more than anthropocentric species-ism to me.
God is impartial! So, He is not anthropocentric too. God and His kindness are all in spiritual form. When the base is the spirit of God or the unconditional love of God, we focus on Grace of God instead of the species of nature. So, a human being is no more a species. A human being is transformed to Son of God in His Grace unlike the animals.
Though, we do not give priority based awareness in God's Grace, we also do not believe in illusions and nature is an illusion. Human being is no more an animal when transformed spiritually by the Grace of God because then he is transformed to the spirit of God. Thus, the spirit of God is not an animal and hence human being is not more an animal too. In this stage of transformation, we learn to love truly and not partially.
Partial love believes in nature and its variety of species, whereas, God's Grace is ONE and has no variety and species. Animals have soul, which is partial, however, a Grace-Human Being has no soul, but spirit only.