From a political point of view, I think Focus Fusion may help in actually reducing the proliferation of nuclear weapons.
Consider what is going on in Iran, for example. Iran has a legitimate argument for wanting to develop nuclear energy plants, as it has been predicted that in the coming decades Iran’s oil supply won’t even be able to meet the needs of its citizens, much less an export market. However, given the background of the government and the political tensions in the area, western leaders are extremely worried about Iran developing a nuclear capability. It has been shown that they have already engaged in uranium enrichment and have not been completely truthful in the past.
It is highly doubtful that Iran will be willing to give up its nuclear program, even in the face of outside pressure. The rest of the world doesn’t have a big enough carrot to give Iran to keep it from doing so, and Iran doesn’t seem to care about anyone’s big sticks. But what if Focus Fusion were working today? Developing a costly, dangerous nuclear fission power plant would seem stupid if you could use Focus Fusion instead, and Iran would have no basis to develop any, unless it were willing to tip its hand to show a different agenda than providing for its citizens. Western nations could offer to help fund the cost of a Focus Fusion rollout for Iran, and Iran could do nothing but accept, or lose all face in the international community.