These guys are just spouting propaganda from "Myths & Facts", a talking points screed prepared by ultra-zionists, and distributed widely for free.

Don't even bother engaging with nonsense like this. It doesn't really matter when the name "Palestine" originated, or whether it has any applicability to any given situation.

What matters is the right to self-determination. Even assuming (solely for the sake of argument) that "Palestinian" was a term adopted only yesterday by the people in the occupied territories, that doesn't affect their right to self-determination. That right is inherent in their humanity (the same holds true for the Israeli people.)

Both peoples have the right to self-determination, whatever the history of the terminology used by them. An attack on Palestinian self-determination is an attack on the very principle of determination. These people are so blinded by their bias that they apparently don't realize that the arguments they make would de-legitimize the claim the Israeli people have to self-determination.