Actually... he may say he distributes for medicinal (i dont remember him saying that) but in reality he supplies seeds to many, many cash crop growers who will grow pounds of weed, sell it to a dealer, who then distributes the weed to normal people. SO you should be able to see why the US is detaining him, he is basically one of the roots, part of this marijuana network or "tree". It doesn't really matter though because there are still 20+ european and canadian seed dealing websites in full operation, and I don't see any reason the european ones will get shut down.
And to sim, thats a pretty weak argument that marijuana is the cause of many deaths due to gang violence. Gangs fighting is due to living in a run-down community, poverty, and having no guidence. Most gangs probably dont even fuck with weed though, coke is must more profitable.