Martin Luther King Jr. said and fought for some things that any right-thinking Christian should applaud.
There are, however, two and only two kinds of people in this world. Those from every nation, tribe, kindred, and tongue who have been born dead in the first man Adam (that would be everybody except Jesus Christ), and those who have been born again from this death in Adam to new and everlasting life in the man born God, Jesus of Nazareth.
God does not differentiate His created moral agents by which paint job He gave us OR how many or what great things we accomplish… or not. Those who are His are in Christ and those who are not, are not.
If I am to take the ancient Christian Scriptures seriously, as understood by centuries of Church history, including William Wilberforce and Hannah Moore, King’s denial of literally every defining Gospel doctrine, the life of serial unrepentant immorality and substantial plagiarism of his doctoral thesis would, if he were anyone else, force me to conclude that whatever else he may have been, “Christian” is not one of them.