There is a respectful and civil (even if clearly wrong) case to make against gay marriage, or against abortion, or in favor of a hard-line towards Iran. But in each case, Warren opts for the most hateful, not respectful, rhetoric to defend his position.
Adding to this, there are also literally thousands of evangelical pastors in America -- even liberal ones! -- who haven't compared same-sex marriage to kiddie rape. Invite one of them. Not one of the crazy ones.