Every choice that a human being has made or will ever make is quite understandable, given the beliefs and perception of that person at that time. All choices are understandable. Not necessarily desirable or preferable, but understandable.
If what you are trying to do is maintain an image of some sort, either in your own eyes or in the eyes of others, then perhaps attacking someone - physically or verbally - makes perfect sense.
When self-preservation or ego-preservation is your priority, it is very difficult to choose love. Love is not, generally speaking, an enticing option in such cases. There is little obvious benefit in trying to love someone who is angry at you, in looking for love in a situation involving fear or anger or judgment. If, in such situations, the defense of the self is the first priority, then reacting defensively or even aggressively is quite understandable.
The questions worth asking in such situations include: What are you defending? What is it that is actually being threatened? Why do you feel the need to react to something someone else has done or said?
If you can take a step back and assess the situation, you can perhaps realize that there is nothing to defend, no need to battle a perceived foe. It is simply a game, and you don't have to play that game if you don't want to. It is simply a choice.
But if you, at that moment, are incapable of seeing things clearly, and are unable to extract your ego and your self-image from that situation, then perhaps you must become defensive, and maybe even lash out in anger and aggression.
Which is quite understandable.
Not necessarily desirable or preferable, but understandable.