When the DL says this, they don't think he really means it, any more than they thought Obama really meant it when he opposed same-sex marriage--they were correct concerning Obama, and since the DL doesn't have any political power in the US, they aren't concerned with the DL's prohibition. Pope Francis is different, because the Catholic Church is still perceived as having some political pull in the US.
They are correct, however, that the Dalai Lama has very little pull inside the U.S. There are a number of Americans who describe their religious beliefs as "Buddhist" in order to be hip and trendy, but I doubt they really follow or deeply understand traditional Buddhism. More likely they just like to toss around the label, have an excuse to do yoga classes, and claim to be spiritual without having to accept God or religious dogmas.
It would be interesting to see how liberal American "Buddhists" who profess to be followers of the Dalai Lama (Richard Gere, etc.) would react if they were ever confronted with the Dalai Lama's beliefs on abortion and homosexuality, and asked whether or not they accept it.