Competition of ideas.
What competition of ideas? That's the wrong answer. The answer is ignorance and irrationality. Rational people fear the influence, advance, triumph, and tyranny of ignorance, for very good reasons. This is based on the history of human behavior under the influence of ignorance, superstition, irrational fear, and religious fanaticism.
Evolutionists and global warming advocates fear competition of ideas which is why they bristle at anyone challenging their ideas and demand that only their viewpoints be taught to children.