If someone gives advice that leads to injury of those who heed it, is the person liable for damages? Or is it the fault of the injured party for trusting a person giving bad advice who was simply exercising their freedom of speech?

Professional licensing is a way to limit liability by adherence to established guidelines, rules, and standards. The person seeking a license could still exercise their freedom of speech, but would not have the backing of an organization that uses licensing and accreditation to establish trust in their members.