Banning all Muslim immigrants may well reduce domestic terrorism (and even that assumption is highly suspect, since a strong anti-Muslim bias built into our immigration laws may actually cause more hostility and terrorism by Muslims already in America).
Still blaming everyone on Earth for Muslims committing terrorism except the Muslims themselves, I see.
But completely ignored in the "ban Muslim immigrants" mantra is the fact that immigrants bring large benefits to America. If you stop all Muslim immigration, you also prevent all of the benefits those immigrants would bring to America. For example, how many lives would be lost each year because Muslims who would become fine physicians or nurses or psychiatrists or researchers aren't allowed to immigrate? How many good jobs would be lost because Muslims who would become successful entrepreneurs aren't allowed to immigrate?
People generally recognize that, for example, we tolerate the 35,000 deaths caused by car accidents each year because the benefits that cars provide outweigh that loss. But Trump supporters are apparently so frightened by the prospect that - say - 30 American might lose their lives each year to domestic terrorists that they will happily forego all the benefits those banned immigrants would have brought. Are they insane?
Because they provide no benefits whatsoever. When you get back to Earth, let us know.