While I respect Trump's desicion due to the games being played by Iran and the terms of the deal: I have never believed that we should interfere with other countries development of nukes. After all only one country has ever used them on people and they did so before the threat of retailiation. Seventy five years later we still have not seen WW 3. Nuke countries tend not to get invaded so maybe more of them would be good?
Pulling the trigger on nukes means you and your legacy are instantly dead. Thankfully world leaders tend to be too very self centered which prevents them from pulling that trigger. On the other hand don't corner them. It would make proxy wars much harder to wage perhaps.