Honestly, 1% of the Bitcoin makes a huge amount. It is a cause of worry if this amount is being used for illegal purposes.
It does make a huge amount but considering the fact that fiat and gold have been used for hundreds of years for illegal activities makes it small.It should not be taken as a demerit of Bitcoin as it is in the hands of people as to how they use the technology.
Such Criminals also use mobile phones to communicate but that doesn't mean that the majority of the population stop using mobile phones.
Actually Bitcoin can be easily used for illegal transactions because of its anonymous nature.
Actually, Bitcoin is pseudo-anonymous and does not guarantee 100% anonymity because each and every transaction gets registered on public ledger.Though, one might use coin tumblers or other cryptocoins with improved anonymity features.
Being not controlled by central authority, the chances of frauds and scams also increases. Also currently the victims cannot seek relief from the courts which further encourages the scammers for doing illegal activities.
This is one sphere where because as most governments don't accept bitcoins as legal tender of money, court cases might not work out, but increasing awareness amongst the people should be the driving force for the government to accept bitcoin and do justice accordingly. 
