Arguments are soldiers. Once you know which side you're on, you must support all arguments of that side, and attack all arguments that appear to favor the enemy side; otherwise it's like stabbing your soldiers in the back - providing aid and comfort to the enemy. People who would be level-headed about evenhandedly weighing all sides of an issue in their professional life as scientists, can suddenly turn into slogan-chanting zombies when there's a Blue or Green position on an issue.
Arguments as soldiers is an alternate label for a conceptual metaphor which is more commonly stated as "Argument is War/Battle". This metaphor is at the core of the adversarial system of debate which is widespread in politics, law and academia. However, it is immature to hold on to this framework for private or deliberative decision making:
Identifying yourself with a side in a political debate may be detrimental to rational evaluation of arguments. Arguments get treated as soldiers, weapons to be used to defend your side of the debate, and to attack the other side. They are no longer instruments of the truth.