The Dalai Lama image was helped by the fact that he was the icon against Communism especially during the period of 1950s to 1980s ie during the cold war when the free world lacks an effective method to counter communism. There was a time during the 1950s and 1960s that communism managed to infiltrate all strata of Americans society that resulted in persecution known as "McCarthyism" refer link :
http://en.wikipedia.org/wiki/McCarthyism.When the Dalai Lama fled Tibet in 1959, he became the perfect tool for the West especially the Americans to counter the communist ideology and during the tumultuous years of the Chinese Cultural Revolution (1966-1976), the Dalai Lama became even more the poster boy of the Americans.
But since the late 1980s and early 1990s, China's communism is no longer a threat to the West. In the last 2 decades China has emerged to become the 2nd largest economy in the world and soon to be the largest in the world. So, the Dalai Lama has become a convenient tool once again to the West to put political pressure on China. Basically, now it is all about power and money; all it always has been; but from a different angle.
The Dalai Lama has conveniently played along with this and in the process spread Buddhism to the West especially. How the ban affected this goal, we can all see for ourselves. Not everything is perfect and many suffered because of the ban and the ban has to be lifted eventually. But this is samsara and the play of the Boddhisattvas is had to understand.