<<Look how often we heard, Lynden Baines Johnson.... wonder how many of them there were.>>
I just conducted an unscientific poll of my own by visiting the home page of the NY Post and doing a search for recent mentions of "President Johnson" (taking no steps to exclude Andrew Johnson, 17th Prez) and got six hits, one of which turned out to be Pres. Ellen Johnson of Liberia. Of the other five, one turned out to be a reference to a football player named Johnson and the other four were LBJ. Three of the remaining four named LBJ as either Lyndon Johnson or Lyndon B. Johnson, one only used all three names. The one that used the full middle name had a valid reason for so doing: It was about the love of initialling, how Mrs. J. ("Lady Bird") and the daughters were also LBJ's, etc. Conclusion: Absent a particular reason for giving a middle name, a middle name will not be used for the 36th President of the United States.
"Franklin Delano Roosevelt" has a certain sonorous ring to it, and I kind of suspect that those who used all three of his names were his friends, not his enemies. There is no conceivable reason for using Delano as a term of opprobrium.
One simple test of innocent intent is to count all the times the name "Hussein" is used when referring to Obama. How many times by enemies or opponents, how many times by supporters or friends. My bet will be that EVERY TIME the name "Hussein" is used, it will be by one of his enemies.