There might be times when righteous indignation could motivate people to correct an injustice. But childish blind anger or temper tantrums with no purpose are the enemy of rational debate.
In part because of the often anonymous culture of social media, we find too many examples of hit and run demagoguery at many levels of debate over political and social issues that are not constructive. The tantrums only reinforce incivility in our public square.
Civility in public discussions is the beneficial product of respect for individuals even if they strongly differ with your own opinions.
Anonymous strangers have no reason to respect each other because they have no idea who they are talking to in many manifestations of the internet culture. Hiding behind an anonymous name might offer some privacy protections, but it also can be an excuse for indulging in intemperate, offensive, and foul language that is never constructive. Is it important to care if our dialogue is civil or not? I think it is. Because without any civility at all, the social fabric breaks down.
The confines of civility does not mean we have to stifle strong debate. But when debates are conducted in a civil manner, we learn more from them about what policy options can best serve the needs of the republic because we can test different ideas on the merits of results rather than against irrational prejudices.
The late University of Illinois trustee Park T. Livingston often said that reasonable people should be allowed to have reasonable differences of opinion and not have their motives attacked at every turn just because they differ. I would only add that not all opinions deserve equal weight in a debate because not all opinions are necessarily informed opinions. Sadly when some people shout "I am entitled to my opinion" they are really just saying "I have an unlimited right to hurl my prejudice and invective at you because i don't like you."
There was a time when debaters in Congress and many state legislatures used deliberately archaic and ornate language beyond the call of normal civility just to keep a debate on a high level that would not stir up emotions. For example, suppose one U.S. Senator and sponsor of a bill might say in a debate, "I appreciate the sincere concerns of my distinguished old friend and esteemed colleague from Montana, but in this case I cannot share his concerns for the following reasons and the safeguards found in the first committee amendment."
That overly-polite language might sound odd and not real to our ears today. But the excessively polite tone makes more sense to advance debate in a civil manner than if the Senator had said instead, "The Senator from Montana is a stupid idiot who cannot understand the bill."
Not only would the senate sponsor lose the vote of the Montana senator on that vote but on many others yet to come as well.