The Greens in Australia came out of state based environmental activism that chrystalised around the Franklin dams issue, but always had a strong social justice component - and yes, the Greens did form from a mixed bag of environmentalists/left/social justice movements. The Greens as a fully developed political party have always had the platforms of conservation, social justice, sustainablity and non-violence/peace. If you don't know this, get educated. If you don't like this, join the Greens and change their platforms or form your own party.
As for their electoral support, this was always inner city trendies - and God love inner-city trendies for being the only folks in Australia to consistently give a **** about environmental issues of this type, because Liberal/National party voters don't seem to care - until it affects something in their own back yard of course. But really it all gets back to your confusion in blaming - sorry, "criticising" - a party that you don't support for not fighting enough for the environmental causes you happen to believe in. Put the blame for the new coal ports where it is deserved - the current Minister for the Environment.