QUOTE(Rick @ Feb 03, 2010, 01:45 PM)
The Luddites were motivated by economics, not by religion, but they were terrorists too.
I don't think it's just the Luddites. Technology itself can be our downfall. Some of Kaku's observations are over-exagerations, though.
There is very little chance that humans could destroy life on earth; even with WMD. If any humans were to survive at all, human progress would only take a small hicup in history, and then move on. If intelligent life were to be destroyed, then the remaining life would probably take a few hundred million years to comeback; or the equivalent of a big hicup in earth's longevity terms.
The key here is the survival of our species, as we are the ones that carry that precious cargo that is our brain. Even if we were to go back to the stone age for awhile.
Now, a scenario like this,
on the other hand, would definitely put an end to our dreams of galactic quest!