Although the ISM is led by the PFLP, the Christian communist wing of the PLO, they still work "in solidarity" with Muslim extremists in the PLO. These people support such expansionism for two reasons:
1)They are panArabists who desire the entire region be all Arab before anything else.
2) They have grown up in a culture based on Jew-hatred.
The ironic thing is that if they succeeded in their goal, eventually they would be eliminated by a Muslim majority. The Muslim Arabs have a saying, "First the Saturday people, then the Sunday people." Christian Arabs in the ISM come from families so inculcated with hatred for Jews they strive to aid the same Muslim factions that later on would destroy them also. Fortunately for these activists, they live in America where they will be safe as Christians in the West Bank would be eventually murdered. Consider the Jew-hatred by thee people as a family tradition imported into the US and exploited by the propaganda ministries of the Palestinian Authority.
Learn more: http://www.conceptwizard.com/pipeline_of_hatred.html