There are different attitudes to respect. Some think it has to be earned. Others think if you don't treat others with respect, then you forfeit the right to any respect from them.
In Germany respect is considered an inalienable human right no matter who you are and what the circumstances, and enshrined in the constitution (I believe there are historical reasons for this). I like living in a country with that attitude, where people mostly remember to treat each other with respect even when they disagree.
Philosophical debates aside, I do think we owe SW the basic amount of respect due to any fellow creature. So on that happy day when he's locked up for crimes against humanity, I think he should still get three meals a day, be allowed to attend to his personal hygiene, and have the occasional visitor as long as he behaves himself and they can find anyone who still wants to have anything to do with him.
I think if we treat him any worse than that, we just diminish ourselves.