[1][2] Passantino lived and worked for most of his adult life in Costa Mesa, California, and received instruction in Christian teaching and practiced as a professing member of the Lutheran Church–Missouri Synod.

He and his soon-to-be wife, Gretchen, had already begun to collaborate in a ministry of Christian evangelism toward adherents of the Jehovah's Witnesses when they became acquainted with the Baptist pastor and countercult writer Walter Martin.

[11] As a couple, the Passantinos began to develop their profile as speakers in evangelical churches delivering presentations about cults and general apologetics questions concerning the existence of God and the historicity of the Bible.

He also contributed a lengthy essay that explored the theory, techniques, and application of religious research to the Evangelical Ministries to New Religions' symposium volume Contend for the Faith that was published in 1992.

[19] In both published essays and books they called into question what they regarded as misconceptions commonly held by Christians about the beliefs and practices of Satanist groups.

[21] Passantino's commitment to a libertarian concept of free agency led to critical evaluations of theological, philosophical, and socio-psychological forms of determinism.

His wife, Gretchen, died from cardiac dysrhythmia as a result of undiagnosed diabetes on October 2, 2014, age 61, at Hoag Hospital Newport Beach.