Why do some atheists go out of their way to give others a bad name?

Just like Fred Phelps gives Christianity a perverted new meaning, those atheists that put up videos of them burning crosses, etc. now give atheists a bad name! I actually have to add a clause that "...but that doesn't mean I burn crosses or worship the devil or anything" when I tell people I'm atheist! What's with these guys?! Same goes for gays, or at least gay stereotypes (wearing flamboyant colors, lisping, etc.).