Everythin is used for q criminal activity, i eon't believe that that fact could hurt bitcoin thqt much on the long run. Thqt fact could slow down btcs progress at the beginning but i believe it wont have any impact later on.
Yes, just because bitcoins are used for criminal activities should not be an argument against bitcoins. Any fiat currency is used for illegal activities and people still don't want to get rid of them.