When George Bush was president he was generally despised in Korea and there were large demonstrations, especially when he visited.
However as a former president he more recently visited Korea to attend a 10 year memorial service for the former president of Korea (he was in office when Bush was president, but committed suicide). Koreans were really happy to see Bush here, despite not liking him while in office and appreciated his speech.
I think holding grudges against retired politicians is odd. Bush is barely noticable on the political scene these days and just gives his opinion or joins events occasionally.