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.
