True, even life is a hypothesis!
At least with the term eco warriors people would have an idea of what you're about. The term Sustainablists doesn't exactly roll off the tongue and would cause more confusion...
Though i do know where you're coming from, as all this focus on Climate Change, while bringing results and moving things forward, is meaning that other issues are being sidelined.
To my mind, sustainability is the key and from that everything else falls into place, including any impact on the climate.