This has been attached to bitcoin even during its early days. Maybe because of the decentralized and private nature of bitcoin. But its not the technology but the bad intentions of the people using it are the ones making bitcoin looks bad.
Bitcoin is a system, if only people are educated they will understand it's very useful for online transaction.
Only if we are educated will we can fully understand what bitcoin is, some people just really make use of bitcoin for their illegal transaction,
it's just like they are also using dollar for the same transaction, so there is no difference and therefore we should not conclude bitcoin is for illegal activity.