wouldn't a benefit be that it is erasing the single thing Atlantis has that Silk Road doesn't?
That would be a benefit, yes, but I don't see Atlantis growing large enough to be a significant threat to Silk Road's market share; I don't even see it becoming large enough to be a real threat to Black Market Reloaded, though I could, of course, be completely wrong on that.
The current benefits of introducing Litecoin aren't big enough for it to be a need; and who knows, perhaps DPR doesn't want to do anything detrimental to Atlantis in its youth. This entire place is about something more than a marketplace - it is about freedom, and the more places that exist for people to go to means that if LE somehow managed to take down one or two of those places, there would still be more!
DPR is a freedom fighter of the digital age. Silk Road is a tool employed by him/her to effect change in the world we live in. With more tools - and perhaps more targets for LE, meaning their resources are spread more thinly - we can achieve more change.
Libertas