My guess is the alumni doesn't really support it and a lot of money comes from the state. As for the parents, they are brainwashed into believing that the California state university system is wonderful (and to a large degree I guess it is), and its inexpensive, so they keep sending their kids there. I'm from Virginia, we have fairly conservative state schools (the state went to federal court to keep VMI single sex) and very conservative private colleges -- this crap would never go over here.
some alumni have signed the petition at the following site:
http://ucdivest.org
"University of California Divestment Petition Website
This online petition has been initiated by faculty at UC Berkeley and includes all of the University of California campuses. The campaign for divestment from Israel follows the precedent set by the anti-Apartheid campaign of the 1980’s, when students, professors, and employees called for an end to university investment in South Africa. By signing this petition, UC faculty, alumni, staff, students, and community members are asking the University to use its influence - political and financial - to pressure Israel to respect the human rights of the Palestinian people. This faculty petition joins other divestment campaigns nationwide, including UC Berkeley's Students For Justice in Palestine divestment petition, which has well over 6,000 signatures."