> Taken literally it's accusing someone of a specific depraved act, but it's also clearly a term of abuse. My guess (not a lawyer!) is that once a term becomes more associated with abuse the more you're protected.

Computer people have this weird notion that courts are like a computer program. If x == "foo" then punishment.

That's not how it works. The use of any specific word does not determine in and of itself if something is an assertion of fact or an assertion of opinion. It depends on how you're using the word.