Then i must be a selfish b*stard. I would rather live with guilt of not stopping people from killing others than to not live at all.
The instinct for self-preservation is perfectly normal. However, people can and do get past it, to achieve heroic things.
"Assistance"? Hehe... unenhanced humans wouldn't be much more than chimps compared to posthumans. This "underground movement" would have to be composed of posthumans only -unenhanced humans wouldn't be able to help, they would rather possibly screw it all and unvoluntarily expose the secrecy of it-, protecting the cause of a parallel inferior race. Not that there's anything wrong with it (like today's activists that protect animals, thanks god they exist, someone has to stand up for animals), but if there is a threat to those in these movements, i would think twice before joining them; is it really worth it? People in Greenpeace don't need to worry about the government's secret agents trying to slay them.... wouldn't be the case in this future possible scenario.
I'm not really sure what the point of this is. That humanity would be unable to defend itself without posthuman protectors? That would probably be the case.
While it is true that animal rights activists don't have to worry about government agents killing them, the brave souls who resisted the Nazis and helped save Jews and other "inferiors" during the Holocaust did. I would hope that future posthumans, exceeding human abilities, would do the very same thing.
That is all assuming that posthumans do, in fact, try to wipe out humanity. I don't believe they will.