Our human civilization is very young. Our governments sometimes resort to the level of discourse more appropriate for 5 year old boys fighting in a sandbox. But apparently some toys look dangerous enough to be put on the shelf and never touched without adult supervision.
There are a bunch of hypotheses about why we have yet to encounter or discover other intelligent life in our galaxy/universe (or, more specifically, the Fermi Paradox). Two seem particularly relevant here:
(a) 'It is the nature of intelligent life to destroy itself': There is some period of technological development where the odds of self-extinction become extremely high (e.g. the relatively recent development of nuclear weapons... for example...).
(b) 'It is the nature of super intelligent life to destroy others': Intelligent species past a certain point of technological capability will destroy other intelligent species as they emerge. A species might undertake such extermination out of expansionist motives or even just rational and prudent self-interest: an intelligent species that has overcome its own self-destructive tendencies might view other advanced species as a potential threat. A highly advanced alien species would also likely be a super-predator (as are humans).
But lately I began wondering how much of it is survivor bias and thinking that we cannot extrapolate this into the future.
Nuclear weapons present a very weird trade-off. On the positive side, I'd argue they greatly reduce the chance of total war between nuclear powers, almost to the point of it being unthinkable. Of course it sucks for whichever country they're fighting a proxy-war in, but better than the whole world I guess. On the other hand, there's a slim chance at any given moment someone will do something crazy or some system will malfunction and every living thing on the planet gets vaporised.
The thing that scares me is the possibility of tactical nukes. As the old saying goes: "one man's big tactical nuke is another man's little strategic nuke". Or something like that...