Archbisop Ignatius Kaigama of Jos made the comments after suspected Islamic militants belonging to the Fulani hersmen attacked and murdered seven people last weekend in the state of Kaduna.
Herdsmen also captured and occupied a number of Christian villages in the region and are preparing to regroup with militants from Boko Haram, according to local media reports.
The Diocese of Kafanchan, located in the state, estimates that more than 800 people have been killed in attacks on villages in the last year and more than $17.5 million in damages have occurred.
The statement from the diocese added that more than 1,400 houses, 16 churches, one school and five cars were destroyed in 53 villages in 2016.
"We are becoming so sadistic that we do not see that such brutality creates a culture of impunity, chaos, anarchy and doom; as if the needless killing by Boko Haram is not enough," said Archbishop Kaigama.
"The manner [in which] lives are being taken right now in southern Kaduna and many other troubled areas of our nation is tantamount to a declaration of war against helpless and innocent Nigerians."
The Archbishop warned that young people were gaining the impression that the lives of others are cheap and can be taken away at a whim.
"When will one Nigerian life matter, or must people be killed in thousands or millions before we realise the humongous damage done to our people?"