So, we should sit back and do nothing?

Well, yes.

So, in Egypt, there was a powerful moderating entity (the military) that mostly kept things from devolving into total chaos. No such entity exists in Libya. I agree that it would be a horrible idea for US troops to set foot on Libyan soil, as there will inevitably be a power vacuum and resulting civil unrest following the insurrection, and an Arab force would be better received and more sensitive to the subtleties of the situation, but I'm completely in favor of the US participating in a multinational no-fly-zone enforcement effort. It's been requested by the rebels and supported by the Arab league. If ever there were a legitimate use of military force, preventing the bombing of civilian protesters qualifies.