US nukes are already much smaller than we could build them, though most of them are over the 50 kiloton figure you give. The US doesn’t build the multi-mega ton super bombs, because with our guidance systems using multiple smaller bombs is much more effective.
And Blalron, claiming that using a nuclear bomb = genocide is just silly. Genocide is the killing off (or attempt to kill off) of an unfavoreded group. Nuclear weapons are essentially really big bombs capable of killing lots of people at once, or taking out large conventional military formations in a single go. Now, you could use nuclear weapons to conduct a genocide, but as Rwanda tought us, you can use machetes as well.
Now, against an extremely fanatical opponent, using nuclear weapons might actually prevent genocide - one or two nuclear weapons would break their will to fight, while if you go in conventionally, they might all fight to the death or jump off a cliff if they think they can’t win.