The University of California, Santa Barbara, is investigating allegations of improper conduct and anti-Semitism against a Jewish professor who compared Israel's treatment of Palestinians to the Holocaust.

Sociology professor William I. Robinson sent an e-mail to 80 of his students in January that contained photos of Jews killed by the Nazis and similar photos of Palestinians killed in the recent Israeli offensive in the Gaza Strip, according to The Los Angeles Times.

The e-mail used the terms concentration camp and genocide when referring to Gaza.

Two Jewish students quit the class and filed complaints. Jewish groups also have complained.

Robinson argues that he was within his rights of academic freedom to challenge students with controversial topics.