Having worked on the inside for a long time, I fully understand that. While there are some cases of medical neglect in prisons, most of the things that are told to outside groups, families and friends are either exaggerated or completely fabricated. I deal with families every day who have been told a lot of outlandish things. Sometimes there is a grain of truth in what they have been told, sometimes not.
One inmate's mother called, very angry about the expensive medical charges that her son incurred for an outside appointment. We don't charge for outside appointments. The son apparently told his mother that he had been charged for a procedure to get her to put money on his books. We also don't turn away inmates for a lack of funds, yet many tell their families that they aren't seen because they don't have money on the books.
Then there are those who call family and claim that they have turned in multiple requests for medical treatment and their requests have been ignored. Invariably, this seems to be inmates with charts six inches thick documenting their "lack" of medical care. The higher the number of requests that they report to the family, the more likelihood that the actual number is zero (I have found this to be the case many times).
Inmates can be very convincing. People who don't know the inside environment tend to believe what they are told, and they don't bother to ask questions as to how much is true, or even if any of it is. It is quite possible that your prospective employer believed that you might have spent time gathering information for the organization that you volunteer with.