Well technically you can.

The major reason for Islamic extremism and its hatred of the west is heavily due to the Soviet and American power struggle in the Middle East. People like Bin Laden and other terrorist leaders used the hatred that drew from the fighting and used it to gain followers for groups that had heavily regressive Islamic views(like thinking that the Quran as needing to be followed word by word)(there are also groups of Christians who view the bible the same way, and thankfully those groups are generally shunned) when in fact before fighting had begun, some of these countries were generally very progressive in terms of Islam.

The fighting left power gaps which were filled by militant groups that wanted to gain power, however when the power gap was filled these groups still existed. These militant groups still wanted power and in turn became terrorist, trying to turn more and more citizens to their cause became easy as many of the people in power were ruthless dictators. This and the fact that the Middle East had been ravaged by war from western countries made many citizens turn to extremism.

Now we have terror groups running around because 5+ generations of Muslims have basically been breed to hate the west and have regressed farther and farther into extremist Islam, because for many that is all they know, the younger generations will never learn any other point of view, other than Kill the west, die for Allah.

Edit: Yes, I think it's a horrible idea to let in Muslim refugees