1.) Some "Syrian refugees" really are decent people fleeing a hellhole. DUHhh-Uhhhhh! What % they are of the total mass of "Syrian refugees" is anyone's guess.
2.) 1.) Some "Syrian refugees" are actually terrorist infiltrators. DUHhh-Uhhhhh!
3.) If, as reported, large numbers of counterfeit and stolen Syrian passports are in circulation, a large % of those using them are up to no good. This should suffice to shut down immigration/asylum to "Syrian refugees". It sucks for those who really are decent people fleeing a hellhole, but as the Paris assault demonstrated, a relative handful of terrorist infiltrators can accomplish great slaughter.
A sane country protects itself and its citizens.