First of all, it is entirely inhumane to keep any person locked away in solitary for any time at all. We are not designed to be all alone, and left all alone for too long almost any human will loose their mind. A whole year in isolation is enough to make a very sane and functional person completely mad. It is very reasonable for prisoners to protest against this practice with every tool they have.
Second of all, even prisoners should have the right to refuse food if they want to. Everyone should have the right even to end their life if they so choose, especially adults. After all, if a person cannot decide what to do with their life, is it their life at all? This kind of prison practice makes capital punishment look humane.