The statement is far more to do with Kissinger's beliefs surrounding theories of international relations than to do with Jews and Jewishness specifically. Kissinger is (he's still kicking) a hard core realist. That someone who subscribes to the realist theory of international relations characterised heavily by a focus on the state as the primary actor in international politics, that the international system is anarchic in nature and not truly controlled with any system or over arching authority (downplaying the role of international bodies such as the UN and international law except as a platform and forum for interstate relations and power) and power politics as the best way to both interpret the actions of state and as a guide for decision making that in the long term will produce the most successful policy. For much of the cold war it was a fairly popular theory in the United States given that a lot of it is focused around the kinds of power politics matters which deal with great power competition and seeks to prioritise stability through the kinds of balance of power situations.

Over the years there have been a few separate branches of realism and neo-realism such as offensive and defensive realism which would tend to predict and advocate in different ways with the former hypothesising that generally an actor will seek to expand their power base where ever possible unless the cost of doing so is greater that the gains where the latter will generally predict that an actor will usually focus on preserving their power and obtaining security rather than expanding that.

Now this is a particularly extreme application of realism but the general theory would dictate that a state should not base its large foreign policy decisions in humanitarianism at the expense of hard power based decision making. The theorists and practitioners aren't necessarily amoral and may make exceptions in extreme enough cases. But realism as a theory advocates for a relatively amoral approach to understanding international relations with the demands of hard power and national interests generally being placed before humanitarian goals. Whether or not Kissinger with being hyperbolic to underscore his point is hard to say.

Its also worth mentioning that people who share an outlook framed by a specific theory of international relations doesn't mean that they necessarily agree on specific foreign policy decisions either. For example there where realists who did not consider US participation in the Vietnam war to have been what is sometimes described as a war of necessity. Where realists often describe a divide between conflicts between wars of necessity which are necessarily to preserving the power and security of the state and wars of choice which are fought to preserve other ends such as ideological or humanitarian goals. And a realists, particularly defensive realists, would often argue that a state should generally seek only to participate in wars of necessity.