I'm the last one to defend Facebook here but I don't see how designing an atomic bomb is comparable to working for Facebook, regardless of what you think about the morality of each.
However, one might argue that FB is actually worse. It is hard to quantify widespread societal effects and determine if they would have occurred through other channels. The massive privacy violations across the world through FB is another item that is hard to quantify yet 100% morally wrong.
https://www.nti.org/analysis/articles/costs-us-nuclear-weapo...
https://en.wikipedia.org/wiki/Atomic_bombings_of_Hiroshima_a...
I never asserted that Facebook was a positive for society, neither here nor ever in my life. I'm just saying it's a very steep uphill climb to make a convincing argument that it's worse than something that directly caused hundreds of thousands of deaths and cost trillions of dollars.
If we widen the definition slightly to include other social media firms then the most recent phase of chaos in the Middle East (post "Arab Spring") and the rise of ISIS can directly be blamed on FB and Twitter.