It is only a rumor against bitcoin, no one have proof that bitcoin is used for crimes by criminals, maybe in the past in some places it was used for crimes, but now we do are not seeing any place where we hear about that concept the more we hear is bitcoin is a best currency for those who want to earn online money.
Seriously? Have you been living in a cave for the last five years? Dread Pirate Roberts only accepted Bitcoin, got life in prison and made world wide news. Mark Karpeles used Bitcoin to steal a half a billion dollars, also world wide news. I think we've heard a little about crimes revolving around Bitcoin.