Exceptions are fine. Mistakes are ok too. The main point is to stop the majority of the future terrorists from entering. We can deal with the exceptions by keeping tabs on them and especially their religious "leaders".
The policy will be temporary but last until CAIR figures out a system to turn in terrorists and reward and protect anyone who turns in terrorists.
I'm in agreement, however, the delineation may need to centered on specific countries, rather than a particular religion, just so it'll meet with less time-consuming resistance from those who oppose it.
I do wish Trump had instead specified countries, such as no one from (name all that apply), and all visa waivers the EU will be canceled.