It's a Problem of Semantic Networks

[N]o punishment system with a wide enough range of punishment levels is more “cruel” than any other, at least from the convict’s point of view. It is the level of punishment that a convict finds cruel, not the method of implementing it. A prison system is just as cruel as a torture system; it is large punishments, e.g., long prison sentences or severe torture acts, that are cruel, not prison or torture itself.

Robin Hanson, "Prison Is Cruel"