Everything governments say it's illegal or scam must be bad, right?  Right??
So let's say if one day government say that Bitcoin is illegal, or walking in the street is illegal and not safe, or using cash is bad and spread disease, you will have to think for yourself before accepting this.
First they introduce concept of ''dirty'' and ''clean'' bitcoins, people accept it, and circus show is ready to start.
You can use this formula for anything else, just replace ''bitcoin'' with something else.