According to W3Techs, Cloudflare is used for 80.9% of all known reverse proxy endpoints which account for 19.8% of the entire Internet. It’s safe to say it’s used to host both legal and illegal content with that broad of a scope.

They are an American company and must cooperate with law enforcement when abuse is reported. If you’re planning on hosting pirated content, that most definitely violates their terms of service and will get you in trouble.