Inhuman in a sentence as an adjective

Why do some people think they get to decide what level of inhuman treatment is enough that choosing to end one's own life is the rational choice?

Inhuman definitions

adjective

without compunction or human feeling; "in cold blood"; "cold-blooded killing"; "insensate destruction"

See also: cold cold-blooded insensate

adjective

belonging to or resembling something nonhuman; "something dark and inhuman in form"; "a babel of inhuman noises"