Can't you though? Didn't guns and bombs defeat Nazism? Rather than looking at war as a totally different arena from a battle of ideas, I look at it as the last resort, or the escalation, of that same battle. We want to beat dangerous ideas with other ideas and rationality so that we don't have to beat them with guns. But history has shown, by my reading of it at least, that guns can in fact kill them when it comes to that.
Well, most say WWI reparations led to WWII, right? And there are still natizis all around. In the united states even, we just had an attack in SC.
But arguable thats entirely different. The natzi's seized control of the country, and people were happy to drop it once 'it was over', yes?
Do you propose we kill every person that doesn't share your ideology? Because I agree that that would be an extremely effective answer. Round everyone up with violent ideologies, and burn them in big buildings. But its tough to sepparate wheat from chaff. So really, that solution is just killing everyone that believes in any ideology thats different than mine.
Oops, wait, what does that sound like?
Violence only ever begets violence.
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Edit: Further, I'd argue WWII created Israel, wich lead to increased tensions in the middle east, which ultimately lead to IS. So that war didn't defeat anything, it kicked the can farther down the road. They know now that they can't seize power and fight a world war and win, so now, terrorisms forever.
So who really won? IS is todays natzi's. Except we cant just invade the country because they dont have one. They exist nowhere except the hearts and minds of those who believe.