David Brin, an American science-fiction author and astrophysicist.
He is the leading public critic of 'Active SETI' or METI — the practice of deliberately broadcasting messages to extraterrestrials.
He argues, on 'dark forest' reasoning (that unknown aliens could be dangerous), that a small group of self-appointed transmitters is imposing a one-way risk on the entire human race without consent.
He represents the case that a handful of enthusiasts shouldn't be allowed to speak for everyone on Earth in a potentially dangerous cosmic gamble.