Was the Cold War good for humanity?
The answer to this question depends mainly on what you think the world would have been like if the Cold War had not happened. If you envision a world of peace and justice without the Cold War, then that time period was bad for the world. If, on the other hand, you imagine that a world without the Cold War would have led to the spread of communism, then the Cold War was a good thing for humanity.
Peace and justice are surely preferable at all times to conflict. This means that the world would have been better off if there had been peace (with justice) instead of the Cold War. The Cold War killed many people in various wars and conflicts. It helped lead to persecution of innocent people in both communist and non-communist countries. It would have been better if these things had not happened so, in this view, the Cold War was bad for humanity.
But conflict can be preferable to a state of injustice. It may be better for people to go through conflict in the short term in order to avoid having injustice in the long term. For example, it was surely better for Germany to undergo the horrors of WWII than for it to have lived in “peace” for decades under the evils of Nazi rule. We can argue that the Cold War was good for this reason. We can argue that the alternative to the Cold War was having communism spread across the globe. Communism is clearly worse for human beings than capitalism and democracy. If the Cold War saved the world (or many parts of the world) from suffering under communism for the long term, it was a good thing for humankind.
Which of these arguments makes more sense to you?