I didn't say all walk-ins are stalkers.
Ok let's take this real slow.
1. The shop has already had run ins with known stalkers.
2. The shop knows who the stalkers are by FACE.
3. When a punter tries to book through an app or phone call, they can't see his FACE. They wouldn't know if the punter was someone they don't want to do business with.
4. When they force everyone to walk-in only, no phone or app bookings allowed, then everyone has to show their FACE.
4. Anyone who is not a known stalker, walking in and trying to book, will be allowed to book.
5. Anyone who is a known stalker, the moment he walks in and tries to book, he will be thrown out because they know who he is.
I don't know what else I need to explain this if you still do not understand.