While there may have been no terrorist activity on North American soil from those 6 countries singled out by Trump (and also less stringently and more covertly singled out by Obama), I have to wonder at the value of encouraging people to immigrate from countries that have such a horrible record of violence, human rights abuse, abuse of women and so forth.  

People do not escape the context of the society in which they were raised so easily and often transport their values, good and bad, to their new countries and pass them on to their young.  There are many other nations in the world to which it might be more worthwhile to extend an invitation to immigrate. 

By the way, I'm not talking here about legitimate refugees fleeing these countries. The refugee issue in my mind is a completely different one, which is about humanitarian aid, not planned immigration.