You need to read his speech....he is NOT being ecumenical as you charge. He writes:
“This is what brings me to Brigham Young University today. I am not here because I believe we are going to heaven together. I do not believe that. I believe that salvation comes only to those who believe and trust only in Christ and in his substitutionary atonement for salvation. I believe in justification by faith alone, in Christ alone. I love and respect you as friends, and as friends we would speak only what we believe to be true, especially on matters of eternal significance. We inhabit separate and irreconcilable theological worlds, made clear with respect to the doctrine of the Trinity. And yet here I am, and gladly so. We will speak to one another of what we most sincerely believe to be true, precisely because we love and respect one another.”
“I do not believe that we are going to heaven together, but I do believe we may go to jail together. I do not mean to exaggerate, but we are living in the shadow of a great moral revolution that we commonly believe will have grave and devastating human consequences. Your faith has held high the importance of marriage and family. Your theology requires such an affirmation, and it is lovingly lived out by millions of Mormon families. That is why I and my evangelical brothers and sisters are so glad to have Mormon neighbors. We stand together for the natural family, for natural marriage, for the integrity of sexuality within marriage alone, and for the hope of human flourishing.”
Dr. Mohler is making it clear that because Evangelicals and Mormons stand for a traditional Hetereosexual marriage...and sex inside that....we both risk going to jail.
You need to get updated, then. The Mormon church is in full cave-in mode, pushing for the change in the BSA policy and failing to excommunicate others who push so hard on this irreconcilable world view.
You CANNOT be "friends" with what is so utterly debased and pernicious. That is John McCain language, and I reject it outright.