All throughout the Humanist Manifesto you will find critical and direct attacks on traditional Christianity and Christian Theology. They introductions, beliefs and systems they attempt to create are filled with criticism and attempts to sway their readers and believers in their faith away from the God of heaven. Every basic Christian theology they address and attempt to attack with counter arguments for humanity to be their own god. They follow the oldest lie in the Bible, from the Devil, to be your own god, and disobey they one true God.
You will also find they had to redefine their terms multiple times because human morality apart from a divine authority can only contradict itself. This is because morality has to be tied into the divine or it is no longer morality. It becomes 'do whatever you please' because every man is able to do what is right in his own mind, all leading back to the doctrines of the devil written in Alister Crowley's Satanic book of the law.
Humanist Manifesto I Document
Humanist Manifesto II Document
Humanist Manifesto III Document