I would have to admit that the Calvinists on Triablogue come across as angry, belligerent, and obnoxious. Everyone I know who has disputed with them has complained about their discussion tactics. That doesn't mean that you can't learn a great deal from them, or that they have nothing of interest to say. I would have to admit that I might treat a defender of infanticide who avoids the ad hominem better than a Calvinist who shifts from talking about my positions to talking about me. I have a different philosophy of dialogue from them, which makes it difficult for me to discuss this issue with them with much of any enjoyment.
Birch's post mentions their "rules of engagement" in which they justify the use of harsh and judgmental language, even against those claiming to be Christians. In defense of this they might point out that John Wesley's famous sermon Free Grace is loaded with emotional charges and polemical salvoes.
There is a difference, however. Wesley reserves his harsh language for Calvinism, not for Calvinists.
The Triabloggers attack persons as well as doctrines. But I am not saying that all the ad hominems are on one side of this issue. Nor do I think all Calvinists are like the Triabloggers.
Why is there so much anger in the debate about Calvinism? One is the passion-inducing nature of the controversy. Each side thinks that the other is denigrating God by taking the position that they do. Calvinists think that Arminians are turning God into a wimp, and Arminians think that Calvinists are replacing a loving God with an arbitrary tyrant who does what he wants to because he can. Calvinists further think that Arminians are undercutting the authority of Scripture, although Arminians think that their reading rightly divides the word of truth.
Perhaps contrary to what Birch thinks, we don't need any more psychology than this. You do have to show that someone is wrong before you show how (psychologically) they came to be wrong. C. S. Lewis's rule, you know.
The important question, which Birch raises, is how we go about not being angry Calvinists or angry Arminians. In the course of the discussion the other side does say things that tick us off. I think the way we do it is we avoid ad hominem arguments and misrepresentations. That takes work in this controversy, just as it takes in the controversy surrounding atheism.
Whenever the discussion shifts from a position to the people who hold position, the chance of real intellectual progress is pretty much lost.