Buying heroin on the street killed more people than buying it on the darknet. Because you are not in contact with a potentially dangerous dealer and the junkies could get real drugs.

If it is not pure drugs that kill, but impure drugs and the mixture of drugs, then the myth of the heroin overdose can be dangerous. If users had a guaranteed pure supply of heroin which they relied on, there would be little more likelihood of toxic doses than occur with narcotics administered in a hospital. LINK

If you want to read Ulbricht's lawyer's full case in court it is here.

Also there is not only one argument to whether he arranged any murder for hire:

The often-referenced transcripts of Ulbricht allegedly ordering five murders have not been addressed by actual charges, and no evidence has been provided that the individual in those transcripts is in fact Ulbricht.
So no, Ross Ulbricht was not charged with, convicted of, or sentenced for murders-for-hire. He was charged, convicted and sentenced on the seven counts listed at the beginning of this article, and not one, nor all combined, justify a life in prison. LINK