While Martin Luther King Jr wasn't a Marxist, he was infact very critical of capitalism. In a speech to the SCLC, he said:
“The evils of capitalism are as real as the evils of militarism and evils of racism.”
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“The evils of capitalism are as real as the evils of militarism and evils of racism.”
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This is what Dr. King wrote in his notes in 1951
https://kinginstitute.stanford.edu/king-papers/documents/notes-american-capitalism
https://kinginstitute.stanford.edu/king-papers/documents/notes-american-capitalism
“Call it democracy, or call it democratic socialism, but there must be a better distribution of wealth within this country for all God’s children.” https://truthout.org/articles/martin-luther-king-was-a-radical-not-a-saint/
https://www.huffpost.com/entry/the-uncompromising-anti-capitalism-of-martin-luther-king-jr_b_4629609
"In a sense, you could say we’re involved in the class struggle.”
—King to New York Times reporter, 1968
https://www.isreview.org/issues/58/feat-MLK.shtml
—King to New York Times reporter, 1968
https://www.isreview.org/issues/58/feat-MLK.shtml
He also was involved in a poor people's campaign before his assassination. https://kinginstitute.stanford.edu/encyclopedia/poor-peoples-campaign
MARTIN LUTHER KING JR. CELEBRATIONS OVERLOOK HIS CRITIQUES OF CAPITALISM AND MILITARISM https://theintercept.com/2016/01/18/martin-luther-king-jr-celebrations-overlook-his-critiques-of-capitalism-and-militarism/
"King understood racial equality couldn't be achieved within the constraints of capitalism" https://www.washingtonpost.com/outlook/2019/01/21/economic-equality-martin-luther-king-jrs-other-dream/
King believed that a multiracial working-class movement was required to overcome the failings of capitalism. https://inthesetimes.com/article/20839/martin-luther-king-jr-day-socialism-capitalism
Keeanga Yahmahtta Taylor ( @KeeangaYamahtta) on MLK's radical anti-capitalism. https://www.haymarketbooks.org/blogs/100-keeanga-yamahtta-taylor-on-mlk-s-radical-anticapitalism