Yet the first words there say

Misotheism is the "hatred of God"

so that's a different thing.

That's only one (narrow) definition of a god.

To take a well known example, is Loki "good"?

There is no reason to believe that a higher power cares about the concepts of good and evil to begin with. Taking a walk through the woods seems like a morally neutral activity, but all of the insects you crush along the way might view you as evil for what you do to them.

Somewhat off-topic, but there's this line of thought, which multiple Christian thinkers have come up with throughout the centuries, called the Ontological Argument. It basically tries to prove the existence of the Christian God with only pure logic, no axioms involved.

Proofs without axioms don't exist elsewhere, so take the following with a massive grain of salt, but basically it goes:

God is a maximally good being. Existence of a maximally good being is itself good. Therefore, God must exist.

Aside from this being circular reasoning, it also involves a massive axiom: The existence and definition of good vs. bad.

But with your point, we can advance the argument even further:

Defining what's good is good.

That way, we get twice the circular reasoning, but no axioms anymore. 🙃

I'd never heard of them, but I looked them up, and I don't see anything in their declaration of beliefs to suggest that they think that God is bad or evil. They just seem to have an emphasis on praying to Jesus, but they seem to have pretty standard Christian belief that God and Jesus and the Holy Ghost are all parts of the same being.

I am not sure how aligned all of the different Church of God denominations are in their beliefs, but the main website for them seems to be pretty standard Christian stuff.