Theology is an attempt to explain the infinite. Bad theology is an attempt to explain the infinite in a way that makes the infinite look stupid. The classic example of bad theology in the modern world is the notion that
God sends people to
Hell because they sign up for the wrong
religion. This concept is profoundly insulting to pretty much everybody, and it makes God look like a
big jerk. Like other bad theology, this idea saves
atheists the trouble of creating their own
straw man arguments.
Most bad theology is good theology that gets imported to the wrong time and/or place. The only way to avoid bad theology is to realize that each person is going to need to construct a concept of God that they can understand as an ultimate good.
NOTE:Even though I slipped into talking about "God" in this article, the word God is no more integral to theology than any other particular word. However, since it's the term for the ultimate used in my theological tradition, I'm not going to try to avoid it.