Every business has its share of illegal users apart from the normal legal users like us. For eg, some guys like escrow.ms have already been caught for using bitcoins to steal from credit cards of other countries. (this was in the new earlier this year)
Terrorism financing/ drugs/ etc are nothing new for the police, for years they have been financed by fiat currency by gundas and dadas and even bollywood mobsters and now since bitcoins is picking up, they will continue to use both fiat and bitcoins for all these illegal purposes.
As long as we traders are honest there is nothing to fear.
totally agree with you that their is always good and bad features of all things why even you can take gold is also used for illegal activities so does it then belong that gold is only for illegal use their u can see the good feature as used in ornaments and etc., the same way bitcoin if used properly is very good with full security features.