On the off chance that he is serious about spending 4 to 8 years in a job more difficult and dangerous than any job he has ever had, let's look at his proposal to bar Muslims from entering the US. Would this policy actually prevent a terrorist attack?
Let's start by asking how do you tell if someone if Muslim? In most cases, it is hard to tell just by looking. Islam is not a race or a skin color. There are black Muslims in Kenya and Somalia, there are Asian Muslims in Indonesia and the Phillipines, and there are Muslims with blonde hair and blue eyes in Bosnia.
The best way to know is to simply ask. Most Muslims are pretty open about their beliefs, just as most Christians and Jews are. And I would imagine most of them would begrudgingly comply with an order to stay out of the US. But Muslims who would obey US law aren't the ones you should be worried about. An actual terrorist who wanted to get into this country would likely lie about what his religion is.
So any law barring Muslims from entering this country will do nothing to keep us safer. The only reason anyone supports this idea is because they just don't like Muslims.