Since *bad* depends on frame of reference, the main *bad* thing to many people would be the State losing its ability to tax.
In Bitcoin, ownership is knowledge. You either know the keys or you don’t. It’s possible to get up and leave and take all your wealth with you, in your head.
States are accustomed to being able to use physical threats of violence to compel labor. With Bitcoin, the State no longer has this power. Governments will have to give people things they actually want.
For many, this is end-of-the-world-as-we-know-it terrifying. I call it liberty.