The phrase "had given up of his own free will a bright future to return to his people" is ironic because it suggests that Roof had promising prospects in Port-Harcourt as a bicycle repairer’s apprentice. However, the reality is that being a bicycle repairer is not considered a "bright future," which makes the statement sarcastic. The writer subtly mocks the idea that Roof sacrificed something great, implying that his prospects in the city were not as impressive as the phrase suggests.