I know folks who feel and act that way. Although many didn't care for Jimmy Carter's explanation he was correct. It's about race in most cases. Those funny-guys are using any topic with momentum or exposure to demonstrate against what they don't have the guts to say on a sign or are prevented from dispaying.
In the Deep South where the cameras hardly ever go the residents are proud of their prejudice positions and say what they think. If attending a teabagger convention and they have a sign that expresses their true sentiment they are removed from the tea party. You can only use topics around the periphery, you cannot attend with signs that express the real reason you may be attending, so they look silly behind the sign of a Birther but underlying that goofy sign is a product of prejudice.