Their goal is not to redefine the term. Their goal is to hijack the thread, and they are succeeding. The best course of action is to ignore them. We all know they would criticize Palin no matter what she says. If not "blood libel", then something else. Arguing with them is pointless, and prevents any meaningful discussion from happening, which is exactly what they want.
I agree, and have argued the same to no avail.
It is up to the site’s managers if they want to allow the left’s water-boys to remain.