Nobody has the counterfactual answer to this.

Proponents will speak to deterrence and preservation of ‘liberty’/non-despotism, opponents will speak to the very real death toll inflicted by these weapons.

Well, what do the prediction markets think?

Markets are unable to lie (as they are deeply/intrinsically connected to reality).

That's ridiculous, markets can absolutely "lie". Markets are aggregates of particpant sentiment and are wrong if that sentiment is wrong. One clear example is when a company is committing fraud that boosts their stock price.

Human beings, in aggregate, tend to be pretty good at predicting some things that individual humans can't (classic examples being number of objects in a jar or weight of an animal) and markets are a weighted and incentived system that exploits this property.

Prediction markets are better at predicting somethings and worse at others and their fallibility is also dependent on how well they're are structured.

No, markets are connected to whatever information is publicly known at a given point in time. Which can be quite far from the truth.