Tell them they can ride their bike to every place they wish to go.
When they tell you to do it respond, "sorry, I don't take instructions from the ignorant."
They want to get on a website? Sorry no. I thought you wanted to "save the planet".
Yep, I am taking away all your electronic toys and unscrewing the light bulbs in your room.
You're hungry? Have a raw potato. Cook it? You wouldn't want to use any energy would you?
Make them feel stupid rather then "oh so smart".
And stupid should hurt.