马克思给黑人贴上 “白痴” 的标签，在私人信件里，他还经常使用侮辱性的字眼 “黑鬼”。
他称其对手Lassalle为“那个犹太黑鬼”，并很清楚地表明，这不只是针对一个人的蔑称而已：
“对我来说，这一点是绝对清楚的，因为他的头形和头发生长的方式显示，他是那些参加了摩西的出埃及之行的黑鬼的后代，（要不然就是他老妈或奶奶跟黑鬼杂交过）。一方面，他有犹太和德国血统；另一方面，他又是黑人。这样必然会产生一个奇特产品。这家伙的粗鲁也跟黑鬼一样。”
以上引用自:
上述文字出自马克思1862年7月30日写给恩格斯的一封信。此信全文：
http://www.marxists.org/archive/marx/works/1862/letters/62_07_30a.htm
http://www.marxists.org/archive/marx/works/1862/letters/62_07_30a.htm
信中，马克思称Lassalle为“那个犹太黑鬼”：
The Jewish nigger Lassalle who, I'm glad to say, is leaving at the end of this week, has happily lost another 5,000 talers in an ill-judged speculation.
马克思又写道：
It is now quite plain to me — as the shape of his head and the way his hair grows also testify — that he is descended from the negroes who accompanied Moses' flight from Egypt (unless his mother or paternal grandmother interbred with a nigger). Now, this blend of Jewishness and Germanness, on the one hand, and basic negroid stock, on the other, must inevitably give rise to a peculiar product. The fellow's importunity is also nigger-like.
