The more bit coin is used for illegal and harmful trades the worse it is for the future and policy that will be applied to it by governments and banks in the future.
So it's a bad development I think.
I see what you are trying to say, uses like this will be pulled out of the context by our enemies and they will use this against us. This will very well happen, but the truth in my opinion is that we can't influence this at all. I mean people will use Bitcoin for anything if it suits them and if they find it useful. Are drugs and guns in tbjs group? Well probably yes but we can't stop that.
Authorities should just fight all drug dealers, nevertheless of which payment method they are using for getting payed.