Is knowledge the root of all evil?

[Aoi Magi]

hypothetical ... Let's say the Trumpster starts a nuclear fight and invites the whole world to join in...
We destroy ourselves ... (And the universe is peaceful once again)

In retrospect, would we have been better off without the knowledge of e=mc2?
In which case, how and when can we know what knowledge will have a net sum positive effect and which won't?

First the universe never was peaceful, and we humans are too insignificant make any difference on that scale.

As for e=mc2, no, it didn't just create nukes, it enabled us to actually make progress towards the space age, which is a necessity to our survival unless we want to suffer the same fate as the dinosaurs, Man made nukes are nothing compared natural alternatives buzzing past us in space. Also the nuke necessarily ain't bad. Humans were destroying each other quite well without it. In fact knowledge of the nuke and the deterrence it provides is the reason behind the present peace we are all enjoying.

We do not posses absolute knowledge and hence we cannot even be sure about what is net "positive", and that is a pretty subjective term anyway, however the more knowledge we gain the better we can form decisions regarding things contained within the scope and domain of the knowledge. So we must always seek to increase the boundaries of our collective knowledge.