Would you say something or ignore it? (Discipline or Abuse?)

Today my uncle that I’ve never met before came over with his wife and son. The son is the wife step-son because the baby is mixed with White and Black.

The boy was playing around. He slid opened up this glass shelf thing. And was fooling around with the glass things in there. I was telling him to not do that and was grabbing his hand so I could close the door.

The mom suddenly pulled him by the hair and started hitting the top of his head. I was so shocked. This happened twice.

The second time I let him play with chopsticks and she snatched the chopsticks from his hand and smacked him.

Even my older brother witness it as well after I left..

So would you say something to the parents or bite your tongue.