Social tensions can be very helpful in producing a more cohesive environment. Typically, once people find out what all they disagree about and get past those things to find that they'll agree on a generous portion of discussion topics, things tend to simmer out dramatically.
A big problem these forum or discussion boards have is Feds or people working on behalf of IC, as corporate shills and foreign INT agencies.

Hell, the FBI hangs out on that guy Four Chin's website and tries to get people to talk about committing crimes pretty regularly.
The good news is that there are friendlies that gather in these places regularly as well.