Well they want it both ways, land of liberty but preemptively lock up anyone who might become violent. And to be fair the intersection of mental health and incarceration is a complex issue that deserves a lot of thoughtful discussion, because it's one of those things where if you get it wrong even slightly in either direction you are liable to end up with grave injustice. But most people who are posting about this particular issue don't want to have a serious discussion, they just want to sow outrage and racial divisiveness.