That was against a particular country and even then he still allowed for humanitarian outs. We aren't going to let some rich Muslim dude from Britain here to do business because of ISIS? It's not the same argument.
“If this oasis of the world should be overrun, perverted, contaminated, or destroyed, then the last flickering light of humanity will be extinguished,” Senator McCarran said of the law. He was a Democrat.
Now unlike Muslims, Iranians were not necessarily supportive of Islamic terrorism. Many were and are opponents of it. Khomeini didn't represent Iran as a country, but his Islamist allies. So Trump's proposal is far more legitimate than Carter's action. Carter targeted people by nationality. Trump's proposal does so by ideology.
Classifying Iranians as a group is closer to racism than classifying people by a racist supremacist ideology that calls for the mass murder and enslavement of non-Muslims, as ISIS is doing today.