Sanctions against Apartheid South Africa

When the US was being pressured by public around the world to impose sanctions on Apartheid South Africa, many (Democrats and Republicans) in the US Congress demurred and protested and argued that we can't impose sanctions on Apartheid South Africa because that would "hurt the people that we want to help" in South Africa.  How come not a single Democrat or Republican, or liberal or conservative in the US media, argued that sanctions against Iran (which punished a company for mailing a printer's cartridge to Iran) would hurt the people of Iran? Not one.