Initially with all due respects one tries to keep the situation cold by trying to avoid the topic or by not responding
When accusations reaches its peak one has no other option other than to just make your view point .The viewpoint may be termed as arrogance. "Arrogance???" that's when the heat starts building up. Accusations turn into deliberate attempts to poke up old issues.The scene gets more and more muddy by each minute,finally either leading to a walkout or a showdown.
But, all these incidents are ones to laugh about n forget the next day.May be this is what they mean by
forget and forgive