Jerry Johnson is president of something called the Nicene Council, and a raging fundie. As fundies are wont to do, Johnson believes that the end is near, and is actively looking for signs to support that idea. (You can read his “10 signs of God’s judgment upon a nation here, but the web design itself should give you a clue about what you have in store if you decide to do so.) He is also a creationist, and has created some videos using common creationist PRATTs to argue against evolution, which he doesn’t understand at all.
Johnson may, however, be most famous for his anti-Mormon activism. In 2012 Johnson asserted that he would not vote for either Romney or Obama, complained that “the two major parties have given us the choice between voting for the Beast or the False Prophet,” and called the two candidates “twin evils.” He also posted a video explaining “why Mormonism is a cult”.
Diagnosis: Not easy to distinguish from a mass of similar-minded fundamentalists, but that doesn’t make him any less insane. Probably not very influential, though.
Note: I am assuming that he is a different person than president of the NRB Jerry A. Johnson.