Injustice anywhere is a threat to justice everywhere, and this is a clear example of injustice. It's a slippery slope to effectively say, "we sometimes punish the wrong people, but in return we get a very safe society", because how can you feel safe in a society that may, at any time, randomly select you for punishment? It might not be "crime" per se, but when you're locked up, does it really matter if it's all by the book? Doesn't that mean the book is bad?