All that is necessary for the triumph of evil is that good men do nothing.
If somebody is behaving badly, don't let them do their damage. Realize that by not stepping up you are partially responsible for the damage being done to the motivation of whoever is being abused. I'm assuming you care about your community? Then speak up! Often, people who are being rude don't even realize that. It is learning for them too. And if they DID realize it and keep doing it, moderation is a mail or ping away.
Yes, openSUSE has moderation. At the conference it was decided to have a reminder of that on our mailing lists. They now feature a footer which tells you how to contact our mods. We have the guiding principles and if people cross the line, you can refer to them. If whoever crosses the line is new to our community, mail or ping them privately. If they keep doing it, feel free to tell them in public they should stop. If they still don't, ask a moderator...
Yes, we have freedom of speech. But this is our corner of the web and if people want to be assholes, well, let them get their own blog to rant. This also applies to bikeshedding: it does damage, so do something if it happens!