Many Americans fear Muslims, not just Trump, and for good reason. Muslim extremism is not a small problem, there's literally whole countries of Muslims that hate America and pray daily for it's fall. Religion is a powerful thing, especially one that offers 72 virgins as payment for martyring yourself while killing as many innocent men, woman and children as possible. 
Of the Billion+ Muslims in the world, how many are radicalized? No one knows for sure but it's clearly in the tens of millions, possibly hundreds of millions. 
America has had but a small taste of Muslim extremism compared to Europe. When we start to experience the level of attacks that France, Belgium and England have had thanks to their open borders, I think you and the rest of the liberal wing will wish Muslim immigration had been restricted.