Is it true that all the wizard and witches who can do the dark arts or love tha dark arts must be bad?
Actually, I don't think so. For example,Severus snape loved the dark arts very much. However,he was not a bad person. Although he had been a Death eater,he helped Harry potter and he loved Lily very much.
I think that the dark arts is useful but dangerous.If we could use is in a better way,there would be no Voldemort or Bellatrix!