Honk if you love the lord

Bumper Sticker Theology is a tool for religious debate. It allows one without the intelligence, or the will to use intelligence to participate in religious debate by simply memorizing short phrases, and learning to apply these phrases at the appropiate time.

My Karma just ran over your Dogma

When someone finds the words to concisely encapsulate a deeply held belief, they usually write it down. Then, they print thousands of copies, each with a medium-grade adhesive on the back, and stick one on their car, and sell the rest.

Now these clever little tidbits somehow find thier way into the minds of those who subscribe to the same or similar belief system being espoused. Some of these have difficulty at expressing their beliefs, or reasons for believing as they do. With the discovery of a bumper sticker that precisly states what they themselves think they believe, a lot of mental effort and soul-searching is avoided. It is clearly much easier to memorize such tidbits as "No Jesus, No peace. Know Jesus, know peace. " and "Life is short -- pray hard" than to actually engage the brain and do some thinking.

Sign o' the times

Humans have a funny little quirk. It seems the more something is repeated the more it seems true. Even something that can be disproven with a very small mental effort. Another quirk is that more humans will also just let all the other humans enjoy thinking that their error is correct, as long as they are in the majority¹. For some in a "church culture" these Bumper Sticker platitudes are repeated time and time again. With each utterance, the phrase seems to take on more weight, and therefore seems more "true".
Soon, one can construct an entier belief system that can be displayed on the back of a bus.

The main drawback of being a Bumper Sticker Theologian, is that your repitoire of stock phrases only work against another repioire of stock arguments. Religion has been around a long time, and for the same amount of time (minus the few minutes it took to explain religion the first time) there has been religious debate. Many of these arguments have been done time and time again since that day that religion was invented. However, sometimes in religious debate, a most rare creature shows itself: Original Thought. If a Bumper Sticker Theologian ever encounters Original Thought (albeit, this is a rare occurance), all is lost. He should think about going for a drive looking for inspiration.