The question is unnecessarily emotional and anthropomorphizes smallpox - smallpox hates that. The question is really "There is a threat contained in labs in the US and Russia. Should we eliminate it, or hold onto it for future research and as a backup for vaccinations in case of other, undeclared stocks?" This breaks down into a whole set of questions, I guess.

What is the probability of the virus escaping from the labs in Georgia and Siberia? What is the probability that there are undeclared stocks of the virus elsewhere? If the second is greater than the first, don't destroy the stocks because you may need them to recreate the vaccine. If the second is less than the first, by how much? And what is the consensus on risk appetite? How well can you ensure that the stocks really are destroyed if they are so ordered to be?

This should tell you the best answer based on safety.

The next set of questions relate to what can be learned from the current stocks. Is there an active research program? Is there a current list of things to learn, or are we just holding onto it 'in case'? Has there been a case that we were glad to have virus stocks that were previously held to be useless?

If there is no obvious gain from holding onto the stock for research and the most significant threat from the virus is accidental release, then destroy the stocks. Otherwise, hold onto them - you can't recreate the stocks from nothing yet and you can always destroy them later.

My gut tells me that we should hold onto them. I'm always loathe to throw opportunities away and that's really what these stocks represent.