Brendan O'Neill offers some historical context about whether or not we should immediately believe all rape accusations.
Automatic belief of rape accusations was a central principle of the KKK’s war on rape, too. This was one of the things that most shocked Ida B Wells, the early twentieth-century African-American journalist and civil-rights activist. ‘The word of the accuser is held to be true’, she said, which means that ‘the rule of law [is] reversed, and instead of proving the accused to be guilty, the [accused] must prove himself innocent’. Wells and others were startled by the level of belief in the accusers of black men, and by the damning of anyone who dared to question such accusations, which was taken as an attack on the accuser’s ‘virtue’. The great nineteenth-century African-American reformer Frederick Douglass was disturbed by the mob’s instant acceptance of accusations of rape against black men, where ‘the charge once fairly stated, no matter by whom or in what manner, whether well or ill-founded’, was automatically believed. Wells said she was praying that ‘the time may speedily come when no human being shall be condemned without due process of law’. No, rape suspects aren’t lynched today. But, as we can see in everything from the destruction of Bill Cosby’s career to the demand to banish from campus students accused of but not charged with rape, they are often condemned on ‘the word of the accuser’ and ‘without due process of law’. Now, as then, ‘I believe’ is the rallying cry of crusaders against rape, and now, as then, such ‘automatic belief’ reverses the rule of law.
It's always tempting to go with what we "know" to be true, without worrying about pesky things like standards of evidence, due process, and the right to confront your accuser. But throwing those things out doesn't increase justice. It just opens minorities up to abuse from the majority.