The 9/11 hijackers came into this country legally. They had documented history. Certainly one cannot compare pre-9/11 security to post 9/11 security. Have the hijackers arrive today, they most likely would have been identified. The countries on the ban list have no way to vett at todays standards.
At least Trump is doing something. Obama took all comers. Using Jafo's logic, that must be no brain. No liberal tears for Obama's ban on Cuban "immigrants" the day before he left office? Of course not, hypocrisy can't work that way.
The devil is in the details.
"Effective immediately, Cuban nationals who attempt to enter the United States illegally and do not qualify for humanitarian relief will be subject to removal," Obama said. "By taking this step, we are treating Cuban migrants the same way we treat migrants from other countries."
Also, it's well known that Saudi Arabia teaches anti-American sentiment in it's schools and is a state sponsor of terrorism