You are correct, upon my own opinion, or puny “authority” I cannot judge. However, I certainly can discern—looking to the Word of God, who confesses Christ and who doesn’t.
It is ABSURD, that in a post above, a Christian says he simply cannot tell if Hitler was a Christian. OF COURSE HE WAS NOT!!!! Is it judgmental to say: Since he never confessed to being a Christian, AND the fruits of his life CERTAINLY showed him to be demonic....that is in the tens of millions he murdered or misled....”HITLER WAS DEFINITELY NOT A CHRISTIAN”?
Of course King is a different matter. He had some wonderful fruits: Racial justice and desegregation. That is he was a key figure in undoing one of America’s most egregious sins: Racism.
But hey, Thomas Jefferson was a key Founding Father, making America a leader in Freedom and Justice, and representative democracy. 1000 years from now, if the world endures, Jefferson will still be known as a man who greatly influenced the whole world for good. However, Jefferson...like King...in his own words, denied the deity of Christ. Jefferson, like King—and Ghandi—was not a Christian.
Does God use non-Christians to do great goods? OF COURSE. We need to be committed to truth however, and not every “good man” worldly speaking, was a Christian.
You could very well decern WRONG. or not.