You keep focusing on the word ‘defamation,’ but legally it doesn’t matter what you call it. Calling someone a pedophile or rapist in writing is libel, which is a form of defamation — that’s how the law treats it.
Quibbling over semantics doesn’t change the fact that it damages reputation and is actionable. A statement doesn’t have to literally say ‘character’ to be defamatory — the harm to reputation is what counts. So yes, it’s libel, so yes, it’s defamation of character in effect