How is a diverse opinion a threat to democracy?
If the opinion is that there should not be a democracy, then that is a threat to democracy.
Excluding a portion of the population from the polls
They are not excluded. They are free to vote for a party that is in line with the constitution.
its almost exclusively a phenomena specific to the left…
I don’t even know what to say. In which world are the far-right, fascists and nazis known to value opposing views? Are you serious?
Your comment is only technically correct, so I am gonna add to that:
Alfred Nobel did invent dynamite and was also a believer in mutually assured destruction, BUT: those two facts are not directly connected.
Dynamite in itself was not intended for warfare, but for mining. It was still relatively unstable so not really suited for warfare. (TNT, which came around 1900, solved that problem.)
Nobel did invent smokeless powder for warfare and he transformed Bofors into an arms manufacturing company though.
https://www.nobelprize.org/alfred-nobel/alfred-nobels-thoughts-about-war-and-peace/