You can't comprehend it, presumably, because it doesn't actually exist. The consequence of ensuring that Human Rights are universal and inalienable is that, inevitably, they will apply to criminals, or to people you don't like*, but it's still worth preserving their universality. The only qualification that should be required to have access to Human Rights is being human.
This isn't about liking "scum", therefore, but about recognising that "scum" are still humans, however distasteful that is. But by protecting "their" rights, we are in fact protecting "ours".
*understatement.