WARNING: The following post could be offensive to some people. You've been warned.
Take a look at the three graphics below. All three are available as window decals from all kinds of sources on and off the internet. Two of them are obviously crude and sophomoric--regardless of your political views. Why anyone would place them on a vehicle as a "statement" is beyond me. But to the matter at hand, ALL THREE graphics have the following in common: THEY ALL VIOLATE COPYRIGHT INFRINGEMENT LAWS.
Bill Watterson, creator of the Calvin and Hobbes comic strip, never licensed the use of his characters for t-shirts, decals, etc. "He refused to merchandise his creations on the grounds that pasting Calvin and Hobbes images on commercially sold mugs, stickers, and T-shirts would devalue the characters and their personalities." (Source) What that means, folks, is that every one of these images sold or used for commercial purposes is a violation of the law...better put, IT'S STEALING. Plan and simple.
The fact that the center graphic depicts the Calvin character praying (and not urinating on something) doesn't make it right. It's still not authorized by its creator; the person selling the graphic has taken something that doesn't belong to them and used it for profit. And if you have one of these on your car, you're contributing to the theft.
Funny thing: Bill Watterson is an atheist according to most bio websites.