He said social issues like jobs, housing, immigration, economic disparities and the environment must be made "foundations for common efforts rather than of division."
Bishop McElroy flatly criticized free market ideology as a rival to human dignity.
"The fundamental political question of our age is whether our economic structures and systems in the United States will enjoy ever greater freedom or whether they will be located effectively within a juridical structure which seeks to safeguard the dignity of the human person and the common good of our nation," he said.
"In that battle, the tradition of Catholic social teaching is unequivocally on the side of strong governmental and societal protections for the powerless, the worker, the homeless, the hungry, those without decent medical care, the unemployed."
He placed property and wealth in the context of Catholic teaching that sees creation as God's gift to all humanity.
"Wealth is a common heritage, not at its core a right of lineage or acquisition," he said. "For this reason, free markets do not constitute a first principle of economic justice. Their moral worth is instrumental in nature and must be structured by government to accomplish the common good."
The bishop stressed the "intrinsic human rights" to medical care, decent housing, protection of human life, food, and work. These rights are not merely negotiating points to discuss after the free market system has distributed wealth, he said.
"Rather, these rights are basic claims which every man, woman and family has upon our nation as a whole," he said, warning that these rights are being denied to large numbers of people.
Bishop McElroy cited Pope Francis' 2013 apostolic exhortation Evangelii gaudium and its description of an economy that excludes some people from meaningful participation in social, political, and economic life.
The bishop said that statements like "this economy kills" are not simply exaggerations. He suggested many people have known someone the economy has killed: a senior citizen who can't afford medicine or rent; a mother or father who is working two or three jobs and is "really dying because even then they can't provide for their kids;" and young people who turn to drugs, gangs, or suicide because they cannot find a job.
"Now mourn them," he said. "And now call out their name; let all the world know that this economy kills."
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At other times, Bishop McElroy has been outspoken against the proposed removal of a statue of St. Junípero Serra from the U.S. Capitol, and against a California law barring health plans that restrict abortion coverage.
He urged in 2015 an overhaul of the US bishops' voting guide to reflect how Pope Francis has "radically transformed the prioritization of Catholic social teaching and its elements." And following the release of Amoris laetitia, he suggested that the divorced-and-remarried may make a "discernment of conscience" that "God is calling them to return to full participation in the life of the Church and the Eucharist."
In addition to Bishop McElroy, other scheduled speakers at the Modesto conference included Bishop Stephen Blaire of Stockton; Cardinal Peter Turkson, prefect of the Dicastery for Promoting Integral Human Development; Cardinal Joseph Tobin of Newark; Bishop Shelton Fabre of Houma-Thibodaux; Archbishop José Gomez of Los Angeles; and Bishop Oscar Cantú of Las Cruces.
One co-sponsor of the event, PICO Network, came to public attention in August 2016 when a cache of documents attributed to billionaire financier George Soros' Open Society Foundations were hacked and posted to the site DCLeaks.com.
The documents said the foundations committed $650,000 in funds for PICO Network and Faith in Public Life in 2015 to use Pope Francis' visit to the U.S. to influence the 2016 elections and cultivate influence within the Catholic Church.
It claimed the grantees were involved in "the long-term project of shifting the priorities of the U.S. Catholic Church to focus on issues of injustice and oppression" and claimed that some U.S. bishops sought to curb Pope Francis' influence on social justice issues. The documents are not always accurate and erroneously indicated the World Meeting of Popular Movements would take place in 2016, rather than 2017.