Eh, Marx was using it to mock Lasalle, who was definitely a fan of racial theories (just social fash things). Still gross but far from what it has been perceived as.

It's important to note that while Marx and Engels would hold retrograde views in regards to Africans/Asians today, they were progressive in that they believed they could be "elevated" (yuck) to the level of Europeans and join the revolution all the same. This is highlighted when Marx one time differentiated "civilized" African-Americans from their continental counterparts. It's obviously not good now but still.