When I hear that phrase I can only think of one place on earth. Disneyland, the sacred cow to Mormons. Excluding anything in the church, Disneyland is the Shangri-La of Mormonism, especially to Utah Mormons. The genius behind Old Walt's amusement park is the marketing. Growing up, I can remember hearing or seeing the phrase, "The Happiest Place on Earth" with every thing Disney.
My last visit to Disneyland, I saw a mother and her preteen daughter. They were standing by a churro kiosk in California Adventure. The girl had an emotional melt down because she wanted a churro. Her mother wasn't interested in buying one. The exchange happened for a couple of minutes, finally the mother said, "This is suppose to be the happiest place on earth, so be happy!".
As a nonbeliever, I have had many discussions with TBMs. When the discussion begins to challenge their testimony they will always say, "well it makes me happy, and is a good way to live". Checkmate, the discussion is over. They don't have to think critically about the church anymore. Their reasoning skills are turned off. It is very effective because nothing I say will alter their perspective. But are they truly happy?
The indoctrination begins early. As early as 18 months. Songs about following the prophet, God, Book of Mormon, Joseph Smith, etc., are taught to children until memorized. The programming teaches that happiness can only be found inside the church. That only truth comes from the leaders, sin never was happiness, you are a special person, etc. The members are taught, that compared to the rest of the world, only they are truly happy. Everyone else may act happy, but they are actually miserable. Only members of the Mormon church are happy.
The Mormon church is the Disneyland of religion. They teach the members that only they have all truth and that by strictly following their teachings the members can finally be happy. They seem happy on the surface, but it is a shallow happiness. One can never truly be happy as a member because one is never good enough. The members are taught basically that the Mormon church is the "happiest place on earth". That is why when confronted with conflicting information or facts they fall back on, "it makes me happy". The church has even changed the name of the "Plan of Salvation" to the "Plan of Happiness". I guess the church isn't interested in salvation anymore only in peddling out "happiness". So all you Mormons, be happy because we told you so....