Bill Donohue is a curious case. He is the president of the Catholic League for Religious and Civil Rights, a job he takes very seriously. Point is, Donohue cannot, as far as I am aware, reasonably be said to be a crackpot – in the sense that he seems relatively pro-science, not a creationist (well, it is a little unclear), not an AGW denier, not a woo-proponent. But he is still a first-class loon. His screeds are completely insane strings of logical fallacies (so much so that they are excellent fodder for intro to critical thinking student on the first day of class), rabid, hateful and paranoid – as rationalwiki puts it, his rhetoric lies somewhere between Pat Robertson and Fred Phelps.
His topics are usually selected defenses of the Catholic church from all – and, apparently, that means all – allegations, such as their being or having been anti-science and … other things. Here are some clues to his stuff (ok, he is anti-gay-rights, and apparently his argument is the hoary slippery slope one). His devotion to the Catholic church is total, and he has no misgivings about distorting virtually all of history, or any fact, to portray it as ‘whatever you say is good, the Catholic church is better, and the Catholic church is always the exception to anything bad’, as in here.
Donohue is also, among other things, one of Mel Gibson’s staunchest defenders. Donohue on the Passion of Christ: “Hollywood is controlled by secular Jews who hate Christianity in general and Catholicism in particular. It's not a secret, OK? And I'm not afraid to say it. That's why they hate this movie. It's about Jesus Christ, and it's about truth. It's about the messiah.” (more here, and here - beware, this is a crazy one). He is, however, engaged in a personal war with the Simpsons and with Penn and Teller.
In fact, Donohue seems to lack any clear understanding of how things work. I suppose the event referred to is familiar to most; if not you can look it up here. Donohue’s first press release was insane; the second, however is so over the top paranoid and lunatic that it must be seen to be believed.
His main attribute (and favorite argumentative technique) is rage. He was enraged (and looking very silly and stupid) when he was furious that the Empire State Building didn’t celebrate Teresa's birthday (see here - I don’t like linking to fox, but the spectacular display of absence of reasoning skills in Donohue’s rant is too good to pass over). And he and his League went completely unhinged over Lady Gaga's new video in the utterly paranoid screed reported on here. His fatwa envy is also notable.
His defense of priests charged with child abuse threads the line between the hilarious and the scary without much elegance: see here, here, and here.
Diagnosis: Vile and hateful fellow with a notorious persecution complex, and in general utterly insane. His impact is uncertain, but is presumably limited to a small group. He comes across mostly as entertaining for his unbridled anger at everything and everybody.