Is the left loony or more sinister?

I often refer to the left and liberals as being loony or loopy, but I just ran across a web site for a group of environmentalists which may force me to search for a more accurate adjective. Here is the web site of a group which feels we should follow their motto and extinguish ourselves to save the planet.

Phasing out the human race by voluntarily ceasing to breed will allow Earth's biosphere to return to good health. Crowded conditions and resource shortages will improve as we become less dense.