The point is, I'm extremely doubtful that anyone would jump on the Monero train and not have their network severely disrupted by law enforcement if it indeed became the "currency of the darknet". Its simply too small and too poorly secured.
I'd say the odds of that are zero. LE doesn't have any deputised hash power lying around and screwing with a currency just means everyone'll switch to something else.
If XMR really did get some momentum then you can count on Bitcoin maximalists to attack them. They'll attack other Bitcoin iterations so a whole, and much smaller, rival would be too much to resist.
Right, just like the odds are zero that LEO's would have mirrored traffic sent to routers at peering points all over North America. Except it did happen, and was verified later. If they want to fuck up Monero, trust me, they'll get the proper resources to do just that.