Weakness is not a sin. Not knowing your position in the hierarchy is a sin. It is a sin that everyone is capable of making unless they become the absolute strongest. It is this goal that Legion and all of life want to achieve. The ant queen wants freedom and so does the demigod. Only strength brings freedom. Absolute strength brings absolute freedom.
The tree father will not fault the demigod for trying to change his fate. Anyone can do anything including lying to try and save themselves. The demigod might be weak but every living thing will struggle to achieve its freedom. It is the constant of life for life to always try to find a way.