One part legitimate grievance. For instance, black on white crime is a huge problem that is not talked about and not addressed in mainstream discourse. In Philadelphia, a close friend of mine got mugged at gunpoint outside of her apartment. Two blocks away, recently, a twenty-something woman who could have been any of my friends, was mugged, shot, and killed. In another incident, a man fitting my own demographic profile, was mugged, shot and paralyzed, a few blocks away. Elsewhere, a group of yuppies walking home were attacked by a "flash mob" and had the crap beaten out of them ( http://www.phillymag.com/news/2011/06/27/fk-flash-mobs/ ). My friend now fears to go to the grocery store after dark. Young professionals fear sending their kids to public schools because their kids will get beaten up and be made miserable ( see http://thenotebook.org/blog/125398/looking-back-on-racial-vi... or http://www.reddit.com/r/AdviceAnimals/comments/1lfr7l/as_a_n... )
When you have legitimate grievances, and discussion of those grievances is actively suppressed (see http://whitegirlbleedalot.com/ ), then it is easy to get carried away with further conspiracies that are not actually true. That leads us to the next ingredient.
One part pattern-matching that leads to plausible, but false, grievances. For instance, it is undeniably true that "Jews totally run Hollywood" ( see http://articles.latimes.com/2008/dec/19/opinion/oe-stein19 ). It is also arguably true that the output of Hollywood is poisoning our culture and leading to the destruction of our civilization. If you believe those two things, then it is not that much of a leap to believe that Jews are ruining the country. Personally, I believe that Hollywood is poisonous, but I do not blame it on the Jews. I think the Jewish people have a disproportionate number of savvy businessman, they ended up running the studios for historical reasons, and that they are mainly producing the films that people want to see. If Hollywood was run by gentiles, the output would be largely the same. Perhaps the main problem is actually the First Amendment - civilization might not be able to survive the freedom to watch addictive trash on television.
One part tribal instinct. When you feel like you have been lied to, called evil, and excluded, well, you want to find other fellow travelers to bond with. And then the internal dialogue feeds on itself, and it exacerbates the "us-against-them" mentality.
One part general vulgarity due to a break down in character education in our society. My mother has frequently commented on the general rudeness, vulgarity, uncivilness, etc. in recent generations versus when she grew up in the 1950's. I suspect this is not just nostalgia. Especially on the internet, people say awful things.
Put it all together, and Stormfront is what you get.