Well, since you said that what Obama said was all wrong, one can only assume that you have another, far more clever correct plan.
The choices are to do something so potential enlistees will not feel desperate, do nothing at all, and just wait and try to catch them before they leave the country.
Every indication is that when someone with an Arabic or other probable Muslim name tries to buys a ticket for Turkey, Lebanon or perhaps Greece, they do indeed make inquiries about his goals. That is what I hear they are doing, and today I heard how they had detained a Somali guy trying to fly to Istanbul, so I think that is evidence that they are actively trying to prevent Muslim Americans from enlisting. They do track passports and airline tickets and have tons of information about this.
If you have a better plan, then you could indicate what it might be. Otherwise I can only speculate.