He’s saying that they aren’t able to properly weigh out the benefits and consequences of their actions. They have a reason behind wanting to kill and that reaso

He’s saying that they aren’t able to properly weigh out the benefits and consequences of their actions. They have a reason behind wanting to kill and that reason outweighs any other desire, despite knowing the risks of killing people (death, prison, etc) which we can assume far outweigh their motivation.