There have been crooked scientists for sure. We've just seen one in South Korea and of course in my country there's the case of McBride and thalidomide. But you know some of those "mistakes" weren't errors at all, they were corrupt acts. And when it comes to medicines you can look straight at the big pharmaceutical companies that damn well know something's got dangerous side-effects but lie to protect their investments and to protect profits. That's not science, that's mammon doing its ugly best to protect itself.
There is good science and there is bad science. Bad science is when they get it wrong - such as the premature claim a few years ago for "cold fusion". It wasn't. It was bad science because it was carried out badly. Bad science is also when politics corrupts it, as in the case of Trofim Lysenko in Stalin's Soviet Union. Now there's case where bad science and totalitarian politics combined to cause many, many deaths. But that wasn't science, it was ideology gone postal.
Good science is valid. How the knowledge gained from good science is used is probably up to others other than the scientist.
Trust me you wouldn't want to live in a world without science.