It depends on how you take the word private. Private could mean Bitcoin is ours, privately-owned by us. That is in contrast to fiat money which is essentially not ours. Fiat could be in our possession but it is never ours. It is owned by the government, the central bank in particular. If the banks consider our money illegally-earned, they could easily freeze our account and get the money from our individual accounts. Bitcoin is different. It is a private property once it is already ours.