Is bitcoin a criminal tool? Well, it may be. Is a lady stocking a criminal tool? Well, it may be, beacuse it may be used to rob a bank and even worse it may be used to attract males to a female sex-worker.
Do you see how absurd it is even to ask such questions? Even sun glasses may be a criminal tool because they hide one's identity...
You could argue anything is a criminal tool, usd cash has got to be the most widely used criminal tool in the world. At least with bitcoin you are not senseless wasting resources on a piece of paper. With bitcoin there is a trail so if someone finds the transaction it can be traced.