Terrible Atheist Argument #1

[Esquilax]

This assumes that the definition of God is just made up by people. To be fair, this is true, but if you start off by affirming such a position, you're begging the question against theism to begin with, aren't you?

The alternative is that the god described in the MGB concept exists outside of human intervention and imagining, at which point he ceases to actually be the MGB in the first place, since we can always imagine something greater than it.

It might be strange to say, but by definition, the MGB can't be what it is.