I think it is a fair point within the context. It links up with the "NK developing nukes for survival" but it also plays out in the sense that an outside nation of any sort, including our allies, can never be certain that 4 years from now a deal we made will continue to be honored. Iran, Paris agreement, various trade agreements, NATO, etc. have all been brought into questioning as of late. It is impossible for an ally or other country to 100% predict how a vetted agreement will play out once a new administration comes into office. Unfortunate side effect of our system, but I don't think it is a bad system.

No this is absolutely relevant. Part of the reason that the Agreed Framework failed was because of the inconsistency and disagreement between the president and congress. And look at Trump criticizing the Iran deal, which the UN has found Iran is upholding. It's clear that the US will do whatever it wants, regardless of whatever deal you have negotiated with them before. This is literally what Trump ran on.

It's very much on-topic.

You discomfort with certain truths of your own country is not a reason to dismiss what he said.