Stopping issuing visas in itself would be bad for US reputation. I know many Iranians who really work hard to get a visa for the USA to visit the country they long for at least once in their life. As there is no US embassy in Iran (for good reasons, by the way), they usually have to travel to Turkey at least twice. One couple I know came to Germany for two weeks just to get their visa from the American consulate here. They were so freaking happy to visit the USA for two weeks (they just got home a week before inauguration).