Prediction markets are the best way we know of to synthesize the opinions of many parties. They should be protected as a class of economic free speech, but in the US there is an effort to eliminate prediction markets on the most important issues (like the outcome of an election).
Think about what it implies for the government to be against a kind of organized assembly that causes citizens to become more informed and allows individuals to de-risk the outcome of events.
There is zero risk associated with the result.