The arc of the moral universe is long, but it bends toward justice
When Martin Luther King said this, apparently quoting Theodore Parker, it demonstrated how thoroughly his Christianity had already been infected by progressivism.
From a Christian perspective, there is simply no reason to suspect that the world will become more and more just in secular time. The sheep and goats will be with us right until the final judgment.
Parker first coined this phrase over 160 years ago. The time since his death has seen the race for Africa, which included the huge slave work camp called the Belgian Congo, World War I, the Soviet Gulag, the Chinese cultural revolution, the Holocaust, the Killing Fields, the atomic bombing of Hiroshima and Nagasaki, the fire bombing of Dresden…
By any objective reading of history, Parker‘s conviction has been shown as idiotically wrong.