Following Obama's election, many pondered the existence of a "postracial America." However, lingering racial tensions quickly became apparent, and many African-Americans expressed outrage over what they saw as "racial venom" directed at Obama's presidency. In July 2009, prominent African-American Harvard professor Henry Louis Gates, Jr., was arrested at his Cambridge, Massachusetts home by a local police officer, sparking a controversy after Obama stated that the police acted "stupidly" in handling the incident. To reduce tensions, Obama invited Gates and the police officer to the White House in what became known as the "Beer Summit". Several other incidents during Obama's presidency sparked outrage in the African-American community and/or the law enforcement community, and Obama sought to build trust between law enforcement officials and civil rights activists. The acquittal of George Zimmerman following the killing of Trayvon Martin sparked national outrage, leading to Obama giving a speech in which he noted that "Trayvon Martin could have been me 35 years ago." The shooting of Michael Brown in Ferguson, Missouri sparked a wave of protests. These and other events led to the birth of the Black Lives Matter movement, which campaigns against violence and systemic racism toward black people. Some in the law enforcement community criticized Obama's condemnation of racial bias after incidents in which police action led to the death of African-American men, while some racial justice activists criticized Obama's expressions of empathy for the police. Though Obama entered office reluctant to talk about race, by 2014 he began openly discussing the disadvantages faced by many members of minority groups. In a March 2016 Gallup poll, nearly one third of Americans said they worried "a great deal" about race relations, a higher figure than in any previous Gallup poll since 2001.