Nonsense.
Parler was created because Twitter and Facebook were moderating content. If Twitter and Facebook hadn't been moderating hate speech, Parler would not exist. Posting voices and content which is banned on Twitter and Facebook is the single unique "Feature" of Parler.
Over the months, Amazon has been in contact with Parler's management about moderating violent content and speech.
Facebook and Twitter have hosted content which incites violence and hate speech, but it's far less common and they make (often grudging and half assed) efforts to remove it. On Parler, it's accepted, arguably encouraged.