is it simply in the fact that we can't talk to monkeys, and they can't talk to us, that we can sacrifice them for polio destruction and saving human lives?
Uh, I'd say it's more the fact that they're monkeys, not people.
'Common-sense' morality says that animals are less deserving of rights or protection than people. If you want to argue that they're equivalent -- that we ought to extend the same rights to them as to people, or that we should not kill any animals even if it will save human lives -- then it would seem the burden is upon
you to argue why we should treat them the same.
One thing many people don't realize is how few experiments are done on animals like monkeys now. It's incredibly difficult to get approval to do primate research, not to mention very expensive; and so researchers only use them when absolutely necessary. eg,
in Britain:
84% of animal research used rats or mice
7% - fish
5% - birds
less than 1% - dogs, cats, horses, monkeys combined
If you want to reduce animal suffering, I'd say there are far better places to start. I don't know how many rats and mice are killed by poison, traps, etc, compared to those used in research, but I suspect the numbers are comparable -- and those deaths are probably significantly more unpleasant than being knocked by a shot of ketamine+xylazine, like the ones I've seen in neuro labs were.
Vegetarianism seems like a much more logical place to start -- if it's wrong to kill a bunch of rats in the course of lifesaving medical research, certainly it's far worse to kill a ton of cows and chickens just cause you like the way they taste.