Can you point out the specific quotes in question? All I see him is questioning what is the accurate account of deaths in Cambodia by the Khmer Rouge. Pol Pot was a mass murderer, but the U.S. bought him to power. They overthrew the Cambodian Monarchy, installed a puppet government, and carpet bombed the country. This led to Pol Pot's rise to power. If the Soviet Union had overthrown the U.S. Government, and carpet bombed the U.S., and the aftermath was warring bands of killers that murdered and raped and starved people by stealing their food, the Soviet Union would bear responsibility, even if they had abandoned the U.S. before this occurred. Similar to the U.S. and Cambodia. Pol Pot committed the crimes directly, but the U.S. bombing etc., led to it.
Enlighten people such as myself me realize that both sides in the Cold War, the Soviet Union and the United States, were murderous. In fact, all Colonial powers in history are murderers, Britain, Spain, Belgium, Germany, Japan, etc. We are ruled by murderers, and always have been.