In the mid-1980s, he was a leader of Berkeley's Faculty for Full Divestment and president of Harvard-Radcliffe Alumni/-ae Against Apartheid. He actively opposed both the Gulf War of 1991 and the Iraq War of 2003. He vocally supported both the bombing of Yugoslavia in 1999 and the occupation of Afghanistan in 2002. In 2013, he became involved in the alumni wing of the Divest Harvard movement, seeking the university's exit from fossil fuel corporations. He has also been active in a Columbia faculty group supporting such divestment. He actively opposes the Boycott, Divestment and Sanctions movement targeted at Israel.