"Somebody who sticks to his guns can be called a stubborn person or a principled person, it depends on whether you like his ideas or not. You can call somebody whose ideas you don't like an ideologist or a person of ideas. You can call somebody whose actions you don't like a pragmatist if you like them, or an opportunist if you don't."
Source : "The Journal of the Debates in the Convention which Framed the Constitution of the United States, May-September, 1787", Volume 2, as recorded by James Madison, 1908.