Freedom of speech means no law should abridging the freedom of speech by the government. Denise Helms was investigated because of making threats, and if no evidence to link her posting to action, She won't be found violation of law simply because of her words.

She got fired which is totally unrelated to freedom of speech. Her employer has every right to found her speech not acceptable and fire her. She is responsible to what she said.

She is certainly "brainwashed", not by school or the US government though, in the sense that she thought the freedom of speech had given her the free pass to say anything without bearing the responsibility, and that is certainly wrong.