The reason China joined the War was because the US ignored China's warning not to push the war to the Chinese border. He conveniently forgot this important reason as far as China was concerned. From China's national security perspective, China had no choice but to join the war, otherwise China would have to face a hostile powerful army along its border. Maybe to this professor, that would have been an acceptable outcome, just like Wang jing wei (during the anti-Japanese War)became a puppet for the Japanese because he said China was too weak & no match to the Japanese Imperial army.
All countries like to talk about the wars they won. The World War 2 is the best example.
What is winning? If I had a boxing match with the world heavy weight champion- Mike Tyson & we were tie. Who do you think won the match? China never thought it was stronger than the US. Frankly 99% of the world at that time thought Chinese PLA would be crushed by the UN forces led by US. But China did not lose & pushed the UN forces back to the South of the 38 parallel.
This professor said China suffered much bigger losses than the US. Of course, the weaker side would always suffer more losses. During the Japanese occupation of China, Wang jing wei made the same arguement that China would lose more lives if Chinese people fought the Japs.
What is a just war? I have never heard US admit any war that US fought was unjust war-- Vietnam War, Iraqi wars, etc. If US believes it is justified to "defend itself" to start a war in iraq half way around the world, why wouldn't this professor think China was justified to fend off the American army from its border?