How to easily defeat any argument for God

[GrandizerII]

This is the sort of thing I find really baffling about theology is that in trying to make their presupposed God out to be so vastly different from anything else in existence,

The way you write this, you seem to be assuming the psychology of a vast number of people, most of whom are long dead. 

Do you take it for granted that they begin with a "presupposed God" and then have some motivation to make it "vastly different"? 

Rather than imagining the motivations of people from very different times and places, I think it makes more sense to deal with the arguments as given. 

If you just begin with the axiom that lots of people were disingenuous, it looks like an easy way out.

I don't need to do any psychic readings of dead people. Theology itself begins with the assumption that God exists and contains the assumption that God, in order to be God, must not be like other entities in existence.

When/if theologians try to demonstrate God's existence through logic, they would then be doing philosophy, not theology.

From Wikipedia (Theology):

Theology begins with the assumption that the divine exists in some form, such as in physical, supernatural, mental, or social realities, and that evidence for and about it may be found via personal spiritual experiences or historical records of such experiences as documented by others. The study of these assumptions is not part of theology proper but is found in the philosophy of religion, and increasingly through the psychology of religion and neurotheology. Theology then aims to structure and understand these experiences and concepts, and to use them to derive normative prescriptions for how to live our lives.

Theologians use various forms of analysis and argument (experiential, philosophical, ethnographic, historical, and others) to help understand, explain, test, critique, defend or promote any myriad of religious topics. As in philosophy of ethics and case law, arguments often assume the existence of previously resolved questions, and develop by making analogies from them to draw new inferences in new situations.

The study of theology may help a theologian more deeply understand their own religious tradition,[9] another religious tradition,[10] or it may enable them to explore the nature of divinity without reference to any specific tradition. Theology may be used to propagate,[11] reform,[12] or justify a religious tradition or it may be used to compare,[13] challenge (e.g. biblical criticism), or oppose (e.g. irreligion) a religious tradition or world-view. Theology might also help a theologian address some present situation or need through a religious tradition,[14] or to explore possible ways of interpreting the world.[15]

https://en.wikipedia.org/wiki/Theology

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If you break this all down, it's still saying the Good/God is the standard for what's right and wrong. The Holocaust is wrong because of something to do with the Good/God.

That’s true.

It’s sort of like a wife, whose friend has a really good husband, saying to her own husband why can’t you be more like him? As opposed to saying why don’t you arbitrarily do whatever he tells you to do.

But in your analogy, X is right not because of "good husband" but because of something else. It's just that "good husband" is great at upholding X. But if you insist that X is good because of "good husband" then it is arbitrary.