You really should not go around insulting those who take an opposing viewpoint in public debate. The ideal is clear. You treat opponents with respect. You take seriously what they are saying. In responding, you do not cheat, you do not unfairly sum up or characterize what they are saying. You acknowledge facts; you are not entitled to inventing your own facts. Above all, as much as possible, you avoid logical fallacies. You argue logically and cogently. For, that is the only way that the search for truth is advanced, and it is the only way that informed public opinion created. In short, abuse is no argument. Civility in public discourse is a great and worthwhile ideal.
Much of public debate and discussion takes the form of invective. It was always thus; and it seems it will always be thus. The culprits, I suppose, are human passions; those self-same unruly horses that carry us to great heights when we want to achieve something worthwhile. We often become so convinced that we are right that we cannot imagine how anyone would disagree. And when we confront opponents who are as certain as we are that they are right something seems to snap. Faces contort. Abuse and spit fly. No matter how often people are told to calm down, commit to logical reasoning, respect facts… nothing seems to work. A huge chunk of public debate on the great issues of the day is characterized by the trading of insults.
Insults must serve a purpose, otherwise how come all public political cultures have them?