Be sure that if they had a chance with military offensive they would have done it (Israel/US). Like what Israel did with Iraqi and Syrian facilitates. Due to nature of Iran spread facilities, it is extremely difficult to destroy Iran's program with an air strike unless there are boots on the ground and occupation which is clearly not an option. According to best estimates it would only delay the program by one year with the outcome that Iran will actually quit NPT. Moreover, an attack would unite all Iranian to support the government. So in any case, this approach is not going to be toward the objective.

It is also partly wrong to think that sanctions brought Iran to the negotiating table, Iran has always been negotiating. In fact, most of the development of enrichment was done during UN sanction. Sure, people and economy suffered but again the objective was not the collective punishment it was to reduce Iran program which did not work. What caused Iran to accept to limit its program was the fact that the US accepted peaceful program and research nuclear capabilities which is a matter of pride and recognition.

"Insanity: doing the same thing over and over again and expecting different results"

However, I totally agree with you if your approach is to create another North Korea.

Presumably it's an issue of national sovereignty - it is their country, and they are broadly able to do any activities on their land as they see fit, just as the EU and US have seen fit to develop nuclear weapons.

Presumably the alternative is to threaten to invade or impose economic sanctions, but that doesn't seem to me like the beginning of a productive conversation. If anything it might increase the urgency of getting weapons, of any type, to be taken seriously.