Does all rational/scientific thought lead to Nihilism?

Yes, it does. We humans do have a "dark side". We are evil by nature. Some are good but which ones? And because we are "evil", our knowledge can lead us to a "trap". Doubts? A century ago we didn't know how atoms work. If they could be devided and make them "react" [I am no scientist]. When we finally discovered how they work, what did we do with that "knowledge"? We created the atomic and the hydrogen bombs. I laugh at those "humanist intellectuals" who say the knowledge will make us more "humane". Balony. It has made us destructive. And with the sick ego we got, the more I fear humanity. So, yes, science and knowledge may lead us into destruction sooner or later. I am pessimistic, and can't be otherwise. And I guess people can't handle the raw truth with the demerit I got. HA!