Numerous choices of his as Secretary of State were nearly indefensible, sure, but often as a product of his involvement and meticulous work in every foreign affairs matter, where everything had to be exact, and to fit into the grander strategy that he envisioned for the United States.
As one small example: while H.W. Bush was able to show his goodness and his morality by fighting for Taiwan's role in his role as Ambassador to the UN, Kissinger's controversial pro-PRC stance, however much I despise the PRC government today and then, was what was necessary for the time.
His administration's decision in using the rift that already existed between the PRC and the USSR to further pull them away from one another and open up diplomatic relations with the West instead is a major reason that China has become as powerful as it is today, which is an understandable cause of criticism. At the same time, we can't know what would've happened otherwise, but it's easy to imagine that the USSR could have kept up their Iron Curtain much longer, and the Cold War could've gone in a very different direction.
We can look at other controversial decisions like Allende, the Yom Kippur War, and Vietnam in the same light.
These are the hard decisions one grapples with as Secretary of State. Kissinger's own history as a Jewish immigrant who witnessed Nazism led to this rationalistic pessimism, and this idea that the best state we can hope for is teetering on the edge, slowly relieving tension a la detente, and that true utopia is unachievable.
You can disagree with most of his decisions, but to not even consider his advice after all he's experienced seems unwise.
Edit: Questionably cited Taiwan as democratic at the time — it was a military dictatorship as another commenter mentioned. H.W. Bush's decision of supporting the 'true' government of China was the moral, easily swallowed one, that was much more popular with the American public. Taiwan was heralded to the American people as a potential democratic alternative to the PRC, though it was not a democracy at the time, and so citing the decision as supporting democracy is questionable.