But to his congregation at Saddleback Church in Lake Forest, the "Purpose Driven" preacher made it clear that his goal behind every speaking engagement is always the same – for the "global glory of God."
"I invest my time speaking to groups of unbelievers that most pastors never get the opportunity to share with," Warren wrote in a recent update to the Saddleback family.
"Jesus said, 'It is not the healthy who need a doctor, but the sick. I have not come to call the righteous, but sinners,'" Warren added, citing Luke 5:31. "If you want to have a Christ-like ministry, you have to associate with the people Jesus did - unbelievers!"
Though highly popular for his bestselling book, The Purpose Driven Life, and for his influential and wide-reaching ministry, Warren has received a lot of flak in recent years for his association with pro-choice president Barack Obama, his support behind a major initiative to combat global warming in 2005, and for speaking engagements such as the ISNA convention this past weekend.
"Every time I speak to any non-Christian group, I get criticized by well-meaning believers who don't really understand how much Jesus loves lost people. They are more concerned with their own perceived purity than the salvation of those Jesus died for," Warren stated in the letter, which had no specific mention of ISNA but was sent out one week ahead of its convention's kick off.
Critics of Warren's latest appearance include Zionist Jan Markell, founder of Olive Tree Ministries, and fundamentalist Steve McConkey, president of 4 WINDS.
According to McConkey, Warren's "silence on the exclusive claims of Christ" this past Saturday "led his Muslim audience into believing that works will save a person."
"Rick Warren envisions coalition of faith," McConkey wrote on his website following Warren's appearance Saturday evening. "Where in the Bible does it say we are to combine with false religions to do good works? In James 2:14-26, faith in Christ is first and works second. In Warren's theology, works are first and faith is second because as he does his works, he is not telling people that Christ is the only way!"
Markell similarly criticized Warren, expecting the megachurch pastor not to share the gospel during his appearance.
"Why go to a Muslim outfit and not share your faith and not tell them the truth," she posed to OneNewsNow ahead of Warren's appearance.
She also pointed to ISNA's alleged ties to terror and said she does not understand why Warren's denomination, the Southern Baptist Convention, or own congregation has not expressed any concerns about his dealings with the questionable Islamic organization.
In his letter to the Saddleback congregation, however, Warren insisted that if the church wants to have a Christ-like ministry, it has to build relationships of love and respect and trust with unbelievers.
"For many unbelievers, the barrier to salvation is not the credibility of Jesus but our own lack of credibility and love for them," Warren stated.
The megachurch pastor highlighted the evangelism strategy of the apostle Paul, who said "I have become all things to all men, so that I may by all means save some."
"[T]his is the foundation text of our purpose-driven evangelism," Warren stated, referring to 1 Corinthians 9:19-23, "and as a result, we have baptized over 20,000 adult believers in the past ten years."
He added, "One reason so many churches are stagnant is that their evangelism strategy is either unbiblical, unworkable or both. They believe Jesus' message but they ignore the Jesus model of ministry and mission!"
Warren concluded by emphasizing the need to build bridges to influencers in secular culture including those in academics, business, military, sports, health care, media, prisons, entertainment, other faiths, and government.
"If we are to experience a spiritual revival in our culture and if we want to fulfill Jesus' Great Commission in the world, we must build bridges to all of these, and more," Warren stated.
"We build bridges of love - from our hearts to hearts of even those who hate us - so that Jesus can walk across," he concluded. "You cannot win your enemies to Christ. You can only win your friends."
On Saturday, Warren told a crowd of some 8,000 Muslim Americans that he was not interested in interfaith dialogue but in interfaith projects.
"Talk is very cheap. You can talk and talk and talk and never get anything done. Love is something you do," Warren maintained. "It is something we do together."
While recognizing his religious differences with the Muslim crowd, the Southern California preacher called on the members of the two largest faith communities in the world to not only figure out how to live in peace and harmony with each other, but also to find a way to work together for the greater good without compromising each group's convictions.
He also touched on the controversy surrounding his appearance, saying that those who walk down the middle of the road get hit in two directions.
"Actually, it is easier to be an extremist of any kind because then you only have one group of people mad at you," Warren added.
Warren, the founding pastor of Saddleback Church in Lake Forest, Calif., was the only Christian invited to speak at Saturday's evening main session, which organizers described as the "cornerstone" of the convention. Other Christian leaders were invited to speak at the smaller sessions during the July 3-6 event.