I argue the fact Bitcoin and other coins enables crime.
I'll make it really simple for you: would you hire a hitman with a briefcase full of cash, or you'd do a bank wire with subject "for the murder, thanks"?
Think why we don't use bank wires for this.
Now think why anonymous cash transfers are hard internationally.
Now think what Bitcoin is. It's anonymous cash over the Internet.
It's a huge enabler for illegal activities because it's anonymous and decentralized and happens over Internet.
You can spin it any way you wish, but the fact speak if you're a criminal, Bitcoin is automatically the most attractive way for making transactions to you, aside from person to person cash briefcases.
Law is centralized by nature. Because law has to be enforced in a centralized nature. Decentralization and anonymity means you can't apply the law. "Illegal" means therefore NOTHING to Bitcoin.