Some people can insult or hurt without going out of their way; this also needs to be controlled (and such people often leave forums because they think it's boring not hurting people - true story). Insisting on civility is a good standard - civility shows that we are civilised, after all.
That has nothing to do with serious discussion,
Perhaps it does, if serious discussion is deemed to allow subjects that are commonly banned in common areas because they lead to strong feelings - politics and religion, typically. A serious discussion area may explicitly allow these, but have correspondingly more draconian moderation, with offenders banned from posting in that one place if necessary (that's the way at the forum I've been admin of).
The inclination of most of EGF's posters is to not back away from a slight, but meet it head on...which does not work at all on the Internet.
Very true - well, not most posters, actually. Thing is, it takes rather few to damage the atmosphere.