Before epilepsy was understood to be a neurological condition, people believed it was caused by the moon, or by phlegm in the brain. They condemned seizures as evidence of witchcraft or demonic possession, and killed or castrated sufferers to prevent them from passing tainted blood to a new generation.
It is conceiviable for an entity to not have free will but still be consciouss. It feels like something to be that thing. It couldn’t choose their actions but they could experience pain and suffering. I don’t see a reason for such entity to not have rights only because they don’t have free will.