Crime can be funded with anything: from cash,gold,silver to bitcoin. So all these methods can be hardly traced,not only bitcoin. I don't see any major reason why bitcoin price would decrease if it is used in crimes. Most surely us dollars are used in crimes daily and the price doesn't fall right? 
Thats right dude, I think it would be easier to do funded with cash because no one can track it. There will be no evidence and so on. I do not think it's just a bitcoin made for crime funded. But there are many others including cash