Answer:
This is because Dally knows the person who got beat up, he was letting his guard down and getting emotional
Explanation:
Dally could have witnessed so many people get murdered and but this particular one is different. This is especially different for dally considering he knows the person that was being physically abused. It is different when we have a personal history and have been in contact with someone that loses his life. We get emotional when it concerns them such as we could get emotional when we lose a family member.