But fusion reactors would need to use seawater as fuel. Think about the fish! Imagine you're a poor little clownfish minding your own business and all of a sudden you're sucked into some tube and splatted against a filtering screen until the life is sucked out of you. How can you even suggest that fusion reactors are harmless? And don't think you're going to get out of it by shipping the whole human race to Mars. There could be Martian Bacteria you know ... and they have rights too! You humans ... nothing but a bunch of invaders terrorizing poor helpless life on Earth, taking your claws and ripping them into the flesh of otherwise peaceful nature.

(Here's hoping the intentional irony put into that last part is not wasted).