I hope your friend is not getting on his high-horse about this topic.
Thomas S. Monson, is the president of the church, that is correct. Is he infallible? No.
We recognize Thomas S. Monson, as a man as a representative of the Church of Jesus Christ of Latter-day Saints. To us, he is a Prophet, because he is capable of being the mouth-piece of God.
When he speaks, he doesn't ALWAYS speak as God in the flesh. When he says, "I'm staying in bed today because I want to watch Matlock..." This isn't God speaking. When he says, "Let us pray for Jaclyn Boon who is sick, that Heavenly Father may make her feel better," This isn't God speaking.
President Monson, when he speaks in God's name, will say when he actually is.
We believe that men are called by God into the positions they are placed to serve in the church. Our church has councils and meetings and they talk about people that would be best fitting the position. They make a list of people physically/financially/emotionally/etc..... capable of the strain of being a Prophet/Sunday School teacher/ward pianist - ANY function in the church that is volunteer based.
The councils meet again, after praying and fasting about the names and the people, and they compare their feelings and experiences after they've taken every name to God to get a sure decision. Many times - I think actually - most of the time, God answers those prayers. People sometimes come back with the same name, sometimes they don't and they convene some more...
How Thomas S. Monson became President was by this same way. His name was on a list of many other names, there was a council, it was prayed about - and his name was made to stand out as being "the one" to be the President of the church by prayerful consideration and accepting the inspiration that came from God.
People don't succeed each other - though sometimes it does turn out that way that the previous president is replaced by the person directly beneath him in the service latter.
We revere him more than we do the Pope, because he's the President of our church. Just as you would revere the Pope more because he's the leader of your church.
We believe that God talks to all his children, not just "the Mormons."
If the President Monson, ever says ANYTHING that is directly from God and he indicates to us that it is - it's meant to be heard all over the world, it's for you, it's for me, it's for everyone.
We don't recognize the Pope having that type of authority because he wasn't called by God to serve in his ministry. He only succeeded to reach the position he is in. (Other people have gone into this detail and explained it better...so I won't add to an already long answer.)