When you have to make hard choices in life (staying with a partner, maintaining a relationship with a toxic family member, supporting a friend that's behaving in a way you don't approve), it's easy to be on the fence since you will have arguments for and against the decision.

However, once we choose, we tend to incorporate that choice into our narrative as the solution that makes sense, and reinforce it to the point that we end up forgetting there was once an alternative. "I left my wife, it was miserable, I'm so glad I left", etc.

It is good to not forget that there was once a choice to make, the choice wasn't easy, and there were arguments in the other side that could have won.

He has abrasive behaviour due to his circumstances. The author has the choice of overlooking the negatives and empathizing with him (pity), or rejecting his behaviour regardless of why (hate).

Both reactions can be rationalized and he has the ability to choose which way he leans.