I found this site about two months ago, and had never communicated in any similar forum. I am hooked on this place. I disagree with you on a couple of things. I have changed my opinion on a few (non-profound) things as a result of talking with the diverse people here. As one learns, his opinions are likely to change. Some of the posters are very well informed, others have such a strong opinion on some issues that they can discuss them in compelling ways. Course there are quite a few who only want to inflame, like you say, and some who are here just to stroke their egos.
I get mad because of some of the posts, but another reason I like to argue here is I can allow myself time to calm down before responding. I'm not real good at debating in person, sometimes the anger at someone's comment takes over, so talking this way usually helps me stay reasonable and on-message.
Also, there is a benefit. Expressing yourself is necessary and healthy. And here, there are many who will see your posts, and you're going to hear from folks who agree with you, disagree, don't understand you, like your attitude, feel your anger, some who will damn you to Hell. Even the name-callers have a positive function, to me, as some of the most negative responses can be the most fun to respond to, and I like the challenge of causing somebody to curse me when I'm being civil.
