Actually, I think cyclists that ride irresponsibly should be held accountable for their actions. If they put the safety of others at risk, they should be prosecuted to the full extent of the law.

As far as motorists who behave unsocially, I do my best to ignore them. If they flip me off I try to give no reaction whatsoever. It's the drunk and aggressive drivers that worry me and I truly fear every such encounter with such people.