If someone does something truly good, they don't lie to and manipulate the very people they're trying to do good for.

Not effective.This not works usually.

If God does not exist there is no objective truth, only subjective opinion, and literally nothing has any significance outside of the fleeting, subjective here and now.

While I believe God probably exist - you are wrong. Objective truth exists as everyone is connected to another, however its perception - is God existing or not - is purely subjective. At the end nobody can surely know and understand the greater order of things we call "truth".

The objective, abstract, immaterial standards of good and evil cannot exist in a reality that is nothing more than material (matter). Similarly, the laws of logic cannot exist in a universe that is nothing but matter being acted upon by time and chance. These standards of good and evil, along with the laws of logic, exist independently of the material world.

Materialism vs idealism being opposites is philosophy delusion. Matter (form) and idea (movement/change) are bonded each other. Pantheism is more right than dualism.