The deliberate release of the smallpox virus is likely to be devastating. How secure is the virus, really? Could armed terrorists break into a facility and steal the virus? Could whoever looks after it be threatened, blackmailed, or bribed into releasing it into criminal hands? Could a new government come to power and choose to use the virus as an agent of biological warfare?
Of course, these scenarios are extremely unlikely, but they don't have to be probable; for a catastrophe, release needs to happen only once. Are those who would claim that these scenarios could not happen now able to predict that they could not occur 10 or 100 years from now? I doubt that even a historian could predict this, let alone a virologist.
The analogy of nuclear weapons is perhaps relevant. Since the end of the Cold War, the bombs are in the handsof the Ukraine, Belarus, ...
