When some people are angry, they do not make rational decisions. Anger tends to cloud our thinking and if we act at that moment, we may regret it. When you are angry, it is only natural instincts for you to try and defend and justify your feelings.
When we make decisions without a clear head, it may be biased and unrealistic because it is usually under the influence of rage. Almost like how people do things they wouldn't ordinarily do because they are under the influence of drugs and alcohol.
It is best to calm down first. When we think about it later, we may even realize that we have a fair share of whatever query it is that caused a feud. I've acted out of anger before and later I realized that what I did was totally uncalled for.