* Commission head has been critical of Netanyahu in the past * Says he hopes Israel will cooperate with probe * Promises broad investigation of both sides in Gaza war By Luke Baker JERUSALEM, Aug 18 (Reuters) - Even before starting work as chairman of a U.N. human rights commission investigating the Gaza war, Canadian law professor William Schabas has been vilified as an apologist for Iran incapable of setting aside his perceived anti-Israel bias. Full page adverts have been taken out against him in The New York Times, Wall Street Journal and Washington Post, while the Facebook page of Rabbi Shmuley Boteach, a leader of the anti-Schabas campaign, has attracted more than 30,000 "likes". "There is going to be an issue for the commission getting access, getting into Gaza and going to Israel," he told Reuters in an interview, speaking from his home in England, where he is a professor of international law at Middle*** University. "I can't rule it out." In the meantime, Schabas finds himself defending comments he has made criticising Israeli Prime Minister Benjamin Netanyahu, and explaining how can set aside his personal feelings about the Middle East to carry out a balanced investigation.