Because moderate arguments are harder to make.
I was in a lively debate the other day defending Obama's health care plan. And it takes some time for me to defend it because there's a lot to it and my reasons for supporting it (with its flaws) are a bit complicated. In this debate, my friend suggested that if I have to spend so much time defending something, maybe it's wrong? I also sent another person an article that went on for at least 5 pages defending Obama's two years as a president, and he told me he didn't read it because if you can't sum up your position more concisely, if you have to spend that long defending a position, then there may be something wrong with it.
Because the political forces at work are trying to pull you to one extreme or the other
I feel this in my own life a lot. On most issues, I can see good points on both sides and I usually try to find ways to merge these two issues into one. When trying to determine who to vote for, I prefer people who are rationale and reasonable and who seem to have a record of working through compromise with others of different viewpoints.
But its hard because for most people really active in politics, the whole thing becomes a game. Its us verses them, a battle between good and evil. So, right now I happen I find myself being pulled to the left on some issues for very rational reasons, but as I gravitate toward these news sources, its gets easier and easier to be pulled in.
In the end, I just want to believe that most people that run are really pretty outstanding people.
Because an extreme view is just more fun to be passionate about
Gay marriage is a classical example of this. If you're against gay marriage, you are really against it because gay marriage will destroy marriage as we know it. It will depopulate the earth. It will bring about the end of life as we know it. No matter that gays have committed suicide because of bullying inspired by over the top anti-gay rhetoric. No matter that the aids epidemic killed literally thousands through the 1980's who had no institution to support them or guide them toward healthy alternatives.
If you support gay marriage then you really support it. You believe churches who speak out against it are hateful and should lose their tax exempt status.
The moderate view is harder to defend. Of course, I'll say my view is the moderate one :-).
But the church I belong to is taking a complicated view of this complex issue. We have strong religious reasons for being against gay marriage as a religion, but we also have strong religious reasons for being inclusive, compassionate, and charitable toward all.
Bottom line, this issue is complicated and attempts to make it easy tend to be wrong.
Gay marriage is just one issue. I can make the same case for schools, the environment, abortion.
Jon Stewart says it all better than me:
Rally to Restore Sanity.
Loved these quotes:
"We live now in hard times not end times. We can have animous and not be enemies. If we amplify everything, we hear nothing."