It would be easier to counter an extreme like Islamic immigration with an extreme like a total ban, and then open up for exceptions who don’t pose a security risk. Imagine if during WW2 we had an open door policy allowing Nazis to immigrate here, (something that in reality would have been less harmful than our present situation). We may claim we are not at war with Islam, but Islam is always at jihad with non believers, even if that means they are waiting until their numbers are sufficient to act. A zero tolerance of Islam is a good starting point for making exceptions.
We did interment camps for Japanese Americans during WWII.
I don’t think Trump asking for a PAUSE is radical. I think its a mild proposal compared to Interment camps