Is “never should you let your guard down” a thesis statement?

Yes.

Think of a thesis statement as something that you know or believe is true. For instance: "The dog is brown." After you have told this to someone who is blind, you would go on to explain how and why the dog is brown. The thesis is the main topic in a story. After the thesis is stated, you would go on to explain how and why the dog is brown.

the african society basically suffered the consequences of colonization and apartheid directly attacking the black people, first, during the colonialism and its main idea which which "white people" had better rights, affecting   them principally in the right to establish black people in their territories, access to quality education and health services and took away any civil right even to the black people to feel they have the same opportunities as the settlers.

first one is your answer

~coco