The only thing that can be done about that is basically give better counterarguments to refute those claims.
Using a lot of electricity is not inherently bad for the environment, it all depends where the electricity comes from.
Instead of focusing on reducing power consumption, why not tackle the root of the problem and focus on making energy generation more environmentally friendly?
Here's an interesting article:
https://hackernoon.com/bitcoins-energy-consumption-overblown-31a4eded91f3In essence, the Bitcoin protocol has been designed to decrease energy consumption over time. For example, in 2009 the CPU’s used to mine Bitcoins used 1 million times more energy than the current ASICs. These Bitcoin miners will continue to find ways to operate more efficiently and employ cheaper energy available to them, like hydroelectric plants and renewable energy resources.