But if the citizenry, like you said, doesn't care, how can it be a force that the citizenry desires to project?

If the government acted for the citizenry as a whole, then they wouldn't have to ban these transactions. At best, the government imposes the majority view on the minority. I think that in general this is more dangerous than helpful. Imagine that the government, with full support of 80% of all US citizens, banned doing business with anyone of Iranian descent, not just living in Iran. That's not feasible in the current climate, but it's certainly possible. I think I'd prefer it if such laws were fundamentally unenforceable.