I use this scene to explain implicit bias to people. his first instinct is to assume the aliens are violent and the girl is innocent, but instead of acting on those assumptions he takes time to recognize his bias, look at the situation again, and then act. 

I watched this with my dad when I was fairly young, and I remember thinking that this was why he got chosen; before he even really knew what was going on, he didn’t assume that aliens were dangerous monsters.

Many people read this scene that way. I read it as future Agent J being very, very good at bullshitting an excuse for his strategy of “pick target at random”.

What it read to me is that he was in fact bullshitting the reason for his shot, but that he didn’t choose his target at random; he was fed up with the mysterious interview process, and was giving a middle finger to it.

And it’s that independent streak that separated him from the conformist “best of the best of the best” candidates.