I feel sorry for your friend, because a balanced sense of humor can save us from taking ourselves too seriously, and help us see through the pride and pretense of our sinful world.
Did Jesus have a sense of humor? I'm sure He did. Think, for example, of His comment that it was easier for a camel to go through the eye of a needle than for a prideful, selfish rich person to enter heaven (you can read it in Mark 10:25). Can you picture a camel trying to go through the eye of a needle -- without laughing? I doubt it.
Remember, too, that the Bible tells us God laughs at our pride and arrogance: "But you, O Lord, laugh at them; you scoff at all those nations" (Psalm 59:8). The Bible also says the angels in heaven rejoice when someone repents and gives their life to Christ (see Luke 15:10). Heaven is a place of joy, not sorrow.
Don't misunderstand me, however. Life is serious, and someone who laughs about everything fails to see the tragedy and brokenness of a world that has turned its back on God. Jesus undoubtedly smiled when little children were brought to Him -- but He also wept over the sins of Jerusalem (see Mark 10:14; Luke 19:41). We live in a broken, sinful world, and all around us are lives that are broken, as well. Is your heart broken over those around you who don't know Christ, and are you seeking to point them to Him?