There is a vast difference between a "necessary evil" and a "good thing." Evil is not good. But if your grandfather cannot understand how something as evil as the Soviet Union can be used to help bring about the salvation of man, he can never understand why evil exists. Ask the Jews who call their own slaughter, "holocaust." (The word means, "a holy offering.")
"But if your grandfather cannot understand how something as evil as the Soviet Union can be used to help bring about the salvation of man, he can never understand why evil exists. Ask the Jews who call their own slaughter, "holocaust." (The word means, "a holy offering.")"
First, my grandfather has been gone for nearly 27 years. You had no way of knowing that, but it is irrelevant anyway.
Second, I am Jewish. You are wrong in your assessment of why the Nazi's attempted genocide of the Jews has been referred to by a word that means "holy offering." There was nothing holy about it, nor was it an "offering" of any type. I (among many others) would suggest that the word "Holocaust" is highly inappropriate, and that those Jews who use it are religiously ignorant. The correct term is "Shoah," which means "calamity." For more details, see http://explanation-guide.info/meaning/Holocaust.html Go down to the very beginning of the text to see an explanation.
I also disagree that the full extent of Nazi or Soviet-perpetrated evil is necessary for the "salvation of man." This is because each of us obtains our own salvation (or not) depending on our own actions and choices. The vast, vast majority of people don't need to see or hear about tens of millions of other people being slaughtered in order to be able to contrast Good and Evil. In view of that fact, I find it difficult to believe that such an event was allowed by G-d to proceed in order to save a few spiritually dense people. We will probably never know the true reason or reasons for the Shoah - or any similar events - until G-d decides to let us know Himself.