http://www.rainbowminerals.net/smallpox.htm
Here are a couple sites I've found showing a few claims about smallpox are a bit overblown. It's still something to watch for, but I guess it's not as bad as it has been made out to be. I don't know about these sites completely though, since I don't have much experience concerning biological agents. Still a fairly interesting read for me.
And why would you ya know? -wink-
I'm not sure I'd take the word of a naturopath - he has a considerable axe to grind far beyond the issue of smallpox (like taking on the entire medical/pharmaceutical/biological establishment).
Smallpox could still be quite messy ... however there are indeed some countermeasures if you find out about the outbreak in time (including various forms of vaccination). But it's only one of a number of biologicals that might be used - it just makes a good example. It might well not be the most destructive - plus there have been weaponized forms of smallpox that are far deadlier than the natural kind. Because of the characteristics of biological systems (!) you can swipe a sample of it while still leaving the original culture intact - unlike bombs, where you have a definite hole in your inventory if someone steals one.
But smallpox is only the beginning. What if you've managed to find a culture of Spanish flu (thought to have died out after the epidemic in the early 20th century)? Or Ebola or any number of others - perhaps even simultaneously? And unlike a nuclear bomb, the supplies (though not the cultures obviously) can be obtained at any Wal-Mart.
It's possible to be too alarmist but I wouldn't discount the potential danger either. Short of massive numbers of bombs it's probably the easiest way to get a large body count.