The racism, poverty, and evangelical indifference he observed at close hand made a deep impression that led him to write the book, Rich Christians in an Age of Hunger.
Alongside him, twelve other religious and human rights activists from various faiths also signed the ad, acknowledging their differences on key moral and legal issues, including Proposition 8.
[6] Sider published over 30 books and wrote over 100 articles in both religious and secular magazines on a variety of topics including the importance of caring for creation as part of biblical discipleship.
Completely Pro-Life, published in the mid-1980s, calls on Christians to take a consistent life ethic opposing abortion, capital punishment, nuclear weapons, hunger, and other conditions that Sider sees as anti-life.
Churches That Make a Difference (2002) with Phil Olson and Heidi Rolland Unruh provided concrete help to local congregations seeking to combine evangelism and social ministry.
In August 2009, Sider signed a public statement encouraging all Christians to read, wrestle with, and respond to Caritas in Veritate, the social encyclical by Pope Benedict XVI.
Later that year, he also gave his approval to the Manhattan Declaration, calling on Christians not to comply with rules and laws permitting abortion, same-sex marriage and other matters that go against their religious consciences.
Sider's son Theodore is a tenured professor of philosophy at Rutgers who has published over 50 scholarly articles and three books with Oxford University Press.