Nuke total - about 250K, ever. Guns total - average probably at least half a million a year, every year for the entire 20th century, plus a good few thousand every year for the two hundred years prior. Even if you nuked e.g. London off the face of the planet (which would take a good handful of nukes, or a decent-sized H-bomb) you would probably only get the nuke total roughly up to what firearms have clocked up in the last decade. You do realise that the casualties at Hiroshima and Nagasaki added up to about 0.5% of deaths in WW2? Compared to artillery and small arms, nukes are theoretically scary but practically not that big a worry.
As I mentioned earlier, I believe the firebombing of Tokyo alone killed more people than the atomic bombings did. And lots of other cities were attacked the same way.
That’s one! Well, you need a rocket, too. Anyone got a second? Or third?
To help start a nuclear winter to off-set global warming. 
Operation Plowshare was a US gov’t project that studies the feasibilty of using low yield nukes to create lakes or waterways. I believe the Soviets did similar studies.
The Test Ban put the kibosh on all that, but given enough time, I’m sure something would have come of it.
Stir up gas reserves to make them easier to extract, create gas storage underground in a glass shell, cut a harbour or canal out of a large land mass, there’s another three. Makes the surrounding areas a tad hot to live in, but what can you do?
Funny you should mention “rockets”. Years ago I heard of a theory that nuclear explosions could be used to propel space-based vehicles, eventually even for interstellar travel. Wiki has a page on nuclear pulse propulsion.
I’ve seen a couple of references to ‘pure science’ in this thread, but they don’t really apply. The OP was pointing the finger at those scientists who actually built the bomb. While there were some big name scientists working on the Manhattan Project, they were essentially engineers while employed there. They were working at the threshold of physics at the time, but they weren’t experimenting or theorizing, they were designing a weapon of mass destruction.
I think historically, we’ve yet to gain the perspective necessary to judge these men. Personally, I don’t like my morality cut and dried; I think it is interesting that the Manhattan project was an extreme moral and ethical conundrum. Most of these men were torn on whether or not to join the project. Afterward, their lives were filled with a mix of horror and awe at what they’d done.
In Richard Feynman’s memoirs, he explains that he initially decided to join the project in order to keep the Nazis from getting there first. But V-E day came and went and he just kept right on working on this huge bomb without reevaluating his position. I think that’s a moral slip-up, and he did too. He may have decided to keep working anyway, but he didn’t even give it any thought.
Then you’ve got a person like Edward Teller who I’ve always been pretty disgusted with. This is a guy who was an excellent physicist and then decided to stop doing science and spend the rest of his life promoting and advocating bigger and more destructive bombs throughout the cold war.
The argument that it would have been built anyway is a good one, especially when it could have been Nazi Germany that got it first. But after V-E day, when everyone was still working on it, the excuse wasn’t so good. Somebody else might inevitably work out an efficient way to infect the entire North Korean Army with Black Plague, but I’m not going to be a part of it.
At first glance, it might seem like a sliding scale of morality here, with people who turned down a job on the Manhattan Project highest, then those who got out after V-E day, after V-J Day, or not at all respectively lower on that list. That’s how I would have judged them in 1950 or roundabouts. But then you have to look at the effects of their decisions: to date, nuclear bombs seem like an effective deterrent to bloody war, and a shot in the arm to the nuclear power industry.
So maybe the Manhattan project scientists were brave foresighted visionaries, willing to do a morally questionable thing in the hope that humanity would be better off. Maybe they were just good guessers. Or maybe in ten years, nuclear holocaust will wipe out half of humanity and the survivors will curse those black-hearted, rotten, maniac scientists for hundreds of generations.
At the moment, I’m leaning towards the judgment that they were torn, morally conflicted individuals who made a critical choice during a crisis that ended up not being nearly as catastrophic as they feared.
I’m with you on this. I can understand the point in improvisation on a basic design, but to do it with something so destructive seems counter-intuitive.
I can guarantee you that my guns will cause you no harm. Rest easy. 
Can the same be said of Russia’s nukes? 100%?
I don’t think even Putin wants to use Nukes. He might be rattling sabers, but I don’t think he wants to see the Cold War return.
Now two of you have promised not to use your guns on others, but how many guns are there in the US? In the World? How many people have them? How many have died from them over the time that atomic bombs have existed?
Sorry, this OP just seems silly. Especially invoke Albert Einstein. Hitler killed how many millions?
This is an empty promise, though. Target shooting and hunting aside, guns exist as a deterrant: ‘Don’t come in my house, you don’t know if I have one or not and if I do, I can use it on you.’ That’s not to say I think you’re actually going to shoot anybody, but the “my gun won’t hurt you” stuff we’re seeing in this thread really doesn’t hold water.
For the OP to have merit (and I don’t think it does) one would have to show that the world would be a better place without the work of the Manhatten project. Most of us likely consider nuclear weapons inevitable and even without the nuclear scientists named in the OP we would probably still have nukes today. The actions of Hitler and the Nazis, however, was not inevitable and without Hitler there would be many more Jews–among others–who would be alive today.
Ok, let me try again, Mosier, unless you break into my house and I shoot you, I promise that my guns wont harm you in any way.
Is that better?
But the quote was that Mosier was afraid of a specific individual’s guns, not every gun ever made in the world today.
What if someone breaks into your house when you’re not there, steals your guns, and uses them to shoot someone? That a gun exists means it might get used.
Nah:
If that were to happen, which I have already taken measures to prevent, would that gun technically be mine still?
Hey, you paid money for it, providing the incentive for it to be constructed and in support of the industry in general. Every day you choose to not destroy your gun, you accept responsibility for its possible future use.
So you agree that the scientists mentioned in the OP have their own ring of hell?