Most people think it is. Fungibility is the ability to be easily swapped for other things. We can use money to hire people to save souls or slaughter sows; the money doesn’t care. Once it leaves our hands, there is no telling where it goes. We all know that (except some prosecutors).
Suppose you have a good friend named Aloysius, with whom you periodically exchange texts and phone calls. One day, he comes to you and asks to borrow a decent sum of money. He is a good friend and you wish to help but you ask him if you could pay him over time. He agrees and you continue to exchange texts and phones calls about birthday parties, spouses, politics, and sports.
Unknown to you, he uses the money to buy illegal drugs, makes a profit, and returns the money. Are you guilty? Any rational person would say you are not guilty and yet many people are found guilty based on just these circumstances. Somehow, in a court of law, people lose their rationality when the prosecutor tells them to. More and more, if authorities target someone, however innocent, and you can lead them to the conviction of the target, you can be targeted, also, until you give them the testimony they want. Joseph Stalin must be so proud!