The speaker is Michael Oh, the founder of Christ Bible Institute Japan. He is of Korean heritage but grew up in America.
I found a video (plus transcript) that explains more fully his animosity toward Japan, and the process of forgiveness he underwent. The video is of a talk he gave on night 5 of the Urbana missions conference in 2009. The animosity basically comes from what he calls the "Asian holocaust" and particularly Japan's occupation of Korea, in which his family experienced much cruelty at the hands of the Japanese.
In the video, Oh mentions these general facts about Japanese war crimes:
"According to historian Chalmers Johnson as many as 30 million Filipinos, Vietnamese, Cambodians, Indonesians, Koreans, Chinese, and others were slaughtered in Asia during the years of Japanese aggression leading up to and including World War II."
"Japanese scientists tested various chemical and biological weapons such as bubonic plague and anthrax on human victims."
"Women were impregnated by soldiers and doctors, their bellies sliced open, their babies removed, and then experimented upon," which seems to refer to findings of the Women's International War Crimes Tribunal on Japan's Military Sexual Slavery.
"So cruel were Japanese medical experiments that Nazi scientists who visited the facilities vomited from the horror of what they saw."
"Almost 200,000 Korean women, and girls as young as 12 years old, were subject to rape upwards of 100 times per day."
He also mentions that his father was beaten if he used his Korean name and that his grandfather's sister was married off after his family discovered that the Japanese took unmarried girls as comfort women.
I think you're overthinking the general application of "love your enemies," which was clearly intended for all enemies of all kinds. That is, the Christian is supposed to love all who mistreat him; this is the call that Michael Oh responded to by becoming a missionary to Japan. The command is recorded in Matthew 5 and Luke 6. Luke's version (in the NET) says:
Love your enemies, do good to those who hate you, bless those who curse you, pray for those who mistreat you. ... If you love those who love you, what credit is that to you? For even sinners love those who love them. And if you do good to those who do good to you, what credit is that to you? Even sinners do the same. ... But love your enemies, and do good, and lend, expecting nothing back. Then your reward will be great, and you will be sons of the Most High, because he is kind to ungrateful and evil people. Be merciful, just as your Father is merciful.