If we accept, for the sake of argument, that most terrorists are Muslims, then that makes the exclusion of Muslim immigrants, the profiling of Muslims for searches, and the internment of Muslims for the proactive protection of the rest of the population EXACTLY as well reasoned as would be the exclusion of male immigrants, the profiling of men for searches, and the internment of men for the proactive protection of the rest of the population.
Or are you going to argue that it's not true that most terrorists are men?
Even if EVERY SINGLE terrorist was a Muslim, that would STILL not justify taking any action against Muslims as a whole, because 'all terrorists are Muslims' is NOT synonymous with 'all Muslims are terrorists'. Even if the former were true, it is a useless fact, if our goal is to identify who the next European terrorist might be; It cuts the pool of suspects from an unmanageable 700 million to an unmanageable 40 million. What is the plan, to lock up 40 million people in order to get the half dozen who you wanted?
Would you be in favour of the police rounding up the entire population of Atlanta in order to be sure that they caught the guy who was planning the next armed robbery in that city? It's far more likely to be someone from Atlanta than someone from elsewhere, so by your logic, that's a reasonable approach to take.