There are other problems related to Schengen, of course; and you’ll have the “Europhiles” blather on about their sacred “freedom of travel”.
The problem is Europe is and never will be one. This idea of mobile freedom is truly based on memories of past simpler times, like days when you could sleep with your front door open.
Islam can be read as death cult that likes to play nice as their roots grow deep in new lands; but once they get their foot-hold, their demands and cult behavior springs forth all over and you then see the total cancer that has been allowed to fester. This can kill the host, or at least they hope so.