Entrapment has been and always will be a common tactic amongst law enforcement in America.
If they know people wan't prostitutes they will set up fake prostitution stings , if they know people want drugs they will have undercovers selling drugs, if they know people want to launder their illegally gained funds they will set up sting ops that would attract those type of people.
I don't think this is an attack on bitcoin so much, just another example of police going undercover and offering illegal things/services and then see who bites.
In a normal case of entrapment, everyone involved knows the product is illegal. Bitcoin is not illegal.
Unless there's more to this than just selling Bitcoin, which is a commodity, not a recognized form of money that goes through the banking system, this would be setting people up for something they had no reason even to believe was illegal, because this is a completely novel interpretation of the law.
Assuming, that is, that there is nothing more than selling Bitcoin involved here.