A lot of great men have really bad ideas. Tocqueville was remarkable for his time in that he was a vocal supporter of American Indian rights and was justly horrified at American colonial expansion and Southern slavery. But even he wasn’t immune from the appeal of empire building, specifically in regards to France’s incursion into Northern Africa. At a time when bread was becoming the necessary worker food for the exploding factory culture of Europe and Northern America, empires of wheat were replacing empires of spice. America was the world’s breadbasket but Tocqueville thought Algeria could be turned into France’s breadbasket; that with a little bit of inventive agriculture this corner of the Maghreb could be transformed into a stretch of grain to rival the American midwest. To do this, Tocqueville had no problem in calling for the ruthless suppression/extinction of the native Arabs.
Remember, World War 2 and Hitler’s wars of conquest were basically European colonialism turned in on itself. The genocide and oppression generated by the European scramble for Africa, both northern and Sub-Saharan, was ruthless and with little precedent.