> I just don't understand why we have all these adages to convince people that "violence is always wrong", while I'm sure some at least some of the people who say that are actively engaged in building machines designed to kill people.
First: because trusted people having such weaponry is, in expected value, believed to lead to less total violence. Second: because not all such violence is part of what you presumably have in mind when you speak of "ongoing conflict". (Of which there are many; when you speak of "an ongoing conflict" you come across as having a particular agenda, although of course I don't know which.)
> But our country (and a lot of them) were literally founded on political violence. How do people square those 2 ideas?
There is no contradiction and thus nothing to square. People are not responsible for the actions of their ancestors, nor of members of their identity groups, and especially not of the ancestors of members of their identity groups. And there is no contradiction between "the ends don't justify the means" and the ends being just.
> First: because trusted people having such weaponry is, in expected value, believed to lead to less total violence.
Unfortunately "trusted people" don't grow on trees... but those who do grow to the highest positions of power, with the most destructive weaponry under their control, ask for trust with stuff like: "No foreign wars", "I'll end that conflict on day one"... "after bringing prices back down".
With that said, changing the conversation from violence to trust in the ideas and people who control it, is a worthwhile endeavor.
>> The rational conclusion of doomerism is violence
That's quite backwards, violence is an irrational response to today's problems. Demonizing the discussion of those problems as "violence" can't be trusted - if the discussion stops, a rational solution will never be found.