He is referring to the policies of colonialism that were widespread. He was British and visited many of the British colonies, but spent a lot of his time in India. These were all lands that Britain had previously colonized and he is referring to the colonization that was predominantly done by white people from Europe.
They would blame them because they wouldn't be free. The colonies were getting "bettered" because they got technology and similar things, but they were blamed because the colonists didn't have independence and freedom and were stripped of their resources and natural wealth which was common at the time.
Support president Truman's decision to bomb nagasaki cause many people died due to this and the effect is very last long. Also this one bomb in nagasaki caused illnesses for the next 60 years also which led on and continued to make people in bad health.
Also just add some evidence about the amount of deaths. The air pultion levels.
