Now this is an interesting list. I started looking into it, mostly because I was surprised to see Kissingers' name up there. As near as I can tell, this is what is being referenced:
Originally Posted by MildSteel
... Kissinger argued that the West – with its strategy of pulling Ukraine into the orbit of the European Union – was responsible for the crisis by failing to understand Russian sensitivity over Ukraine and making the grave mistake of quickly pushing the confrontation beyond dialogue.
But Kissinger also faulted Putin for his reaction to the crisis. “This does not mean the Russian response was appropriate,” Kissinger said.
Still, Kissinger told Der Spiegel that “a resumption of the Cold War would be a historic tragedy. If a conflict is avoidable, on a basis reflecting morality and security, one should try to avoid it. … We have to remember that Russia is an important part of the international system, and therefore useful in solving all sorts of other crises, for example in the agreement on nuclear proliferation with Iran or over Syria. This has to have preference over a tactical escalation in a specific case."...
I cannot find a single instance of Kissinger stating that a U.S. intervention in Ukraine would have meant or could have meant a nuclear war. All I can find him saying is that we risk sliding back into another Cold War in general, given degrading relations. Even Russian propaganda is not attempting to put the words in his mouth that you are. What I suspect you have done is taken a list of people who generally think that US intervention in Ukraine could go badly, and treated it as a list of people who support the ridiculous claim that sending lethal aid to the Ukrainians (for example, as we did to the Afghan fighters who were opposing the Soviets) would result in a nuclear conflagration. It's also worth noting that Caldicott is a global anti-nuke activist who is not actually a Nobel recipient - but was rather part of an organization (the International Physicians for the Prevention of Nuclear War) that was. A random university professor is, well, sort of laughable. I see you and raise you one Warren Churchill. Jack Matlock doesn't seem to have said that the response would have been nuclear war, either (in fact he thinks Russia should leave Crimea), although he is saying:
...Obama’s “warning” to Putin was ill-advised. Whatever slim hope that Moscow might avoid overt military intervention in Ukraine disappeared when Obama in effect threw down a gauntlet and challenged him. This was not just a mistake of political judgment—it was a failure to understand human psychology—unless, of course, he actually wanted a Russian intervention, which is hard for me to believe....
Which is probably about right. Especially in a post-"Syrian Red Lines" environment. The closest he comes to saying what you are saying he claims is:
...Entirely aside from the principles of the UN Charter, international law, and the Helsinki Final Act, Russia has a treaty commitment to the United States and the United Kingdom to respect Ukraine’s territorial integrity. What it received in return was quite substantial, the possession (for destruction) of the nuclear weapons on Ukrainian territory. Does Russia really want to violate arrangements that allowed us to reduce the danger of nuclear weapons threatening us all? Does Russia think that its current actions will encourage or discourage nuclear proliferation? After all, it will be argued that if Ukraine had not returned its nukes to Russia, Russia would not dare try to grab its territory...
which puts the blame on Russian actions and also doesn't claim that nuclear war was plausible in the event of U.S. aid to the Ukraine.
So.. yeah. Apparently not so much.