International Committee Against Mars Sample Return
This group of paranoid "scientists" (probably the same folks that brought you the "anti cassini because its gunna blow up and plutonium contaminate our atmosphere" oraganization) want to prevent NASA or any other space agency from returning any Mars soil samples to Earth. They are claiming that there is a chance that Mars soil samples contain dormant microbial life. They fear that if terrestrial species were exposed to these Mars invaders that it could spell extinction for us or other species.
Their website provides lots of scientific sounding information, but at the same time is really vague. They make many assumptions and ask lots of hypothetical questions that try to force you to come up with conclusions that make you align with their cause. For instance (from the "planetary protection" page):
"We know that Mars had aqueous epochs in which running water covered portions of the planet. We also have solid evidence that perennial frozen lakes occurred on Mars as well. Indeed the similarities between Mars and Antarctica are remarkable in many areas of study. So why were the highly oxygenated soils of Antarctica not looked at as an analogy for what was happening on Mars with the Viking GEX experiment?"
None of what they talk about has been conclusively proven, but are only theories. There is evidence that supports such theories, but they still remain unproven. They then end the paragraph with a question for the reader, but they never answer it, leaving the reader with the sense of "Hey! Those NASA scientists forgot something!". I'm sure they didn't forget something, or miss something. They wanted to find life.
I just have a hard time respecting an organization that has an image of the Earth with Mars as a biohazard symbol as their logo. Sigh...