"To be valid, a prescription for a controlled substance must be issued for a legitimate medical purpose by a practitioner acting in the usual course of professional practice. The practitioner is responsible for the proper prescribing and dispensing of controlled substances. In addition, a corresponding responsibility rests with the pharmacist who fills the prescription. An order purporting to be a prescription issued not in the usual course of professional treatment or in legitimate and authorized research is not a valid prescription within the meaning and intent of the Controlled Substances Act and the person knowingly filling such a purported prescription, as well as the person issuing it, shall be subject to the penalties provided for violations of the provisions of law relating to controlled substances."
You don't have to stray away from independents. No one is forcing you to verify fake prescriptions or prescriptions that you know are not for legitimate medical purposes.
By the way, there are a lot of really good independents out there. There are many places that follow all the rules, more than even the chains. Places that don't do anything unethical, immoral, or against the law. I'm very glad I found a place which is 100% by the book.