There's definitely a lot of indecision on his part. He's at least acutely aware his grandmother is poisoning people, yet he does nothing to really stop her. It's like he just puts his hands up, and says it's out of his control.
Still I can understand a lot of his actions. It's a really difficult thing to call out a loved one on something illegal, especially one you grew up with your whole life. He really did have at least enough evidence though to at least justify avoiding his grandmother, and preventing his children from ever meeting her.