I am searching for the title of a dystopic future/science fiction novel from the 80's (perhaps early 90's). Earth is overpopulated, resources are near exhausted, etc. One of the premises is that the main antagonist, a messianic saviour type, preaches that the only way to save humanity is if some, if not much, of the population must sacrifice their lives in order to save Earth.
There is a band of protagonists that are on a journey to find something or discover the truth about this antagonist. We discover near the end of the novel that the antagonist's motive behind his philosophy is his intense hatred of humanity. The novel is not Logan's Run.