Simon Bolívar and Che said the same things about many Latin American nations. All of those countries existed and continue to exist. Waxing romantic about "One World" or "One People" doesn't magically alter reality or international law. Your failure to read between those propagandistic lines speaks volumes, however.
You also fail to distinguish between Mohsen and Arafat, or between Mohsen and the Palestinian people on the other. Those folks had something to say about this as well, you know.
Mohsen essentially followed the line of as-Sa'iqa's Syrian-Baathist ideology (Mohsen himself being as-Sa'iqa's leader under the control of the Ba'athist government of Syria under Syrian leader Hafez al-Assad), which interpreted the Palestinian question through a perspective of pan-Arab nationalism - despite the fact that in some respects this contravened the PLO charter, which affirms the existence of a Palestinian people with national rights, corresponding with this it is noted that hostility existed between the main Fatah faction of the PLO under Yasser Arafat and the Syrian Ba'ath party of Hafez al-Assad (which in turn supported Palestinians like Zuheir Mohsen and the Ba'athist as-Sa'iqa faction of the PLO) on this issue. Mohsen himself was in fact both a leader of the Syrian Ba'ath party controlled as-Sa'iqa faction of the PLO and a Palestinian member of the Syrian Ba'ath party's own National Command in the present day nation of Syria itself. Making Zuheir Mohsen uniquely both a PLO leader and an official in the ideologically Pan-Arabist Syrian Ba'ath party at the same time. As such, he stated that there were "no differences between Jordanians, Palestinians, Syrians, and Lebanese", though Palestinian identity would be emphasised for political reasons. This originated in a March 1977 interview with the Dutch newspaper Trouw: