Is it possible to refute this possibility? Theoretically, could it be true? Since we have no way of finding out the truth, what we can do is check which of the two options advances us more.
If we assume that GOD is evil or a liar, we are doomed to a life of constant skepticism, never knowing what is right and what is not, what is moral and what is not, what the meaning of existence is, and what we should do.
Neither religion, nor philosophy, nor science can help us in anything, because everyone can be part of the deception.