Yes they can. They just apply the full pressure of the law and 99.9% of bitcoiners will roll over. 

Professional criminals targeting public facing bitcoiners are just as effective using alternative methods. Anything can and will be taken from anyone. 

Unfortunately I've seen violence up close for a long of time and you'd be surprised just have many people fold even through just the threat of violence. Can't change the sympathathic nervous system. Our will to survive is instinctive.