That does nothing but punish thousands, or, in this case, millions of people who are themselves suffering under that country’s government.
I’ve been to North Korea. I’ve spoken to the people there and seen directly the fear and suffering in their eyes. The DPRK government is terrible. The people there need all the help, love, information, and compassion we can give them.
The real crime is making it illegal to go there and do that.
Could you imagine other, more civilized countries e.g. in Europe jailing their citizens for coming to the US to peacefully speak or present? After all, we run indefinite detention torture prisons all over the world (or, more specifically, human rights criminals in our government do). We (criminals in our government) tap the phone lines and emails. We (criminals in our government) assassinate citizens without trial. We have had thousands of government officials fail to seek justice against our leaders for war crimes. Nearly every accusation that can be leveled against the DPRK government can be leveled against the US government, if at a smaller scale in most cases. How do we do the mental gymnastics to punish normal people simply traveling and teaching because of criminal acts committed by others they have never met?
I agree that the DPRK government is bad, just that I agree that the US government is bad. But a country is absolutely not its government, and punishing normal, peaceful people by the millions who happen to live with the misfortune to be trapped in such places where the leaders are criminals or tolerate criminals amongst themselves, or punishing people who travel to these places to teach and speak is madness.