The point is that our gadgets become more powerful and more potent as weapons; so as we have a good history of past abuses it is sort of easy to extrapolate to the future.

What is still don't understand: would intelligence be an inhibiting factor - like more reasonable Humans are supposedly less destructive; Maybe the same goes for machines.

I don't buy the argument about competition for resources - With enough effort you can always stretch it so that there is enough for everybody/everything.

Another interesting aspect: once upon a time people would become very agitated when discussing politics (that was when we still had ideological differences and when people thought that their stance does matter); In our time we have discussions about sci-fi instead of that.