Well, Biden is trying to improve relations with China and Kissinger is seen as a big friend of China, and he claims to have some influence with the top brass there (China made a big turn towards the west, and Kissingers meetings with Zhou Enlai played some role in it - Mao shaking hands with Nixon was a very big deal in 1971), so there is some alignment ; on the other hand you have a point, Democrats seem to have a very strong negative reaction towards Kissinger.